SPAQ Spartan Energy Acquisition Corp

Filed by Spartan Acquisition Corp. III

pursuant to Rule 425 under the Securities Act of 1933

and deemed filed pursuant to Rule 14a-12

under the Securities Exchange Act of 1934

Subject Company: Spartan Acquisition Corp. III

SEC File No.: 001-40022

Date: November 30, 2021

The Honorable Jane F. Garvey, an Industry Leader and Former U.S. Official, to be Appointed

Chairwoman of Allego Board of Directors

PARIS & ARNHEM, the Netherlands & NEW YORK—(BUSINESS WIRE)—Allego Holding B.V. (“Allego” or the “Company”), a leading pan-European electric vehicle (“EV”) charging network, which recently announced its proposed business combination with Spartan Acquisition Corp. III (NYSE: SPAQ), today confirmed that The Honorable Jane F. Garvey will assume the role of Chairwoman of the Board of Directors of Allego N.V., the combined company, upon the closing of the business combination. Current Chairman of Allego Julien Touati of Meridiam will serve as the Board’s Vice-Chair.

During her career in public service, Ms. Garvey served as the 14^th Administrator of the U.S. Federal Aviation Administration (FAA) under former presidents Bill Clinton and George W. Bush. Her legacy as Administrator includes leading the FAA through one of the most challenging chapters in aviation history in the wake of September 11, 2001, and subsequently restoring America’s confidence in air travel by strengthening airline safety and instituting many modernization milestones. Ms. Garvey also served as Acting Administrator and Deputy Administrator of the Federal Highway Administration (FHWA), where she developed the GARVEE bonds, an innovative financing initiative enabling states to use federal highway funds more effectively. Ms. Garvey was previously director of Boston’s Logan International Airport and she served as Commissioner of the Massachusetts Department of Public Works.

“I’m very pleased to serve as Chairwoman of the Board of Directors of Allego N.V. upon the close of its business combination. Allego is a dynamic, market-leading company that has expanded its network of charging solutions across Europe to establish the blueprint for multi-national EV charging infrastructure development,” commented Ms. Garvey. “Allego’s mission to provide EV charging infrastructure across Europe is advancing the future of electric mobility, and I look forward to working with Allego’s management team and my fellow directors to execute on the Company’s strategic plan and support its long-term, sustainable growth.”

Ms. Garvey has served in numerous high-profile appointments across the public and private sectors that have provided her with a unique and robust set of knowledge about the intricacies of the transportation industry. In 2008, Ms. Garvey served on the transition team for President Barack Obama, helping to advise the new administration on transportation policies. Prior to that, Ms. Garvey advised U.S. public/private partnerships at JPMorgan, specifically advising on financing strategies to facilitate project delivery for state governments. She continues to serve on various corporate boards and commissions.

“We are honored to benefit from Jane’s guidance here at Meridiam, and I am thrilled to continue our partnership on the new Board of Allego N.V.,” said Julien Touati, current Chairman of the Allego Board of Directors and Partner and Corporate Development Director at Meridiam. “We are confident that

Jane’s experience across both public and private operations of the transportation sector will prove invaluable as Allego continues to build out new charging sites and extend the geographic footprint of its EV charging stations across Europe.”

“Allego N.V. is very pleased to expand its Board of Directors by adding a Chairwoman of Jane’s caliber as we prepare for operations as a public company,” said Mathieu Bonnet, Chief Executive Officer of Allego. “We look forward to leveraging Jane’s insights into multiple facets of the transportation industry as we continue to reinforce our leadership position within the European EV charging market.”

About Allego

Allego delivers charging solutions for electric cars, motors, buses and trucks, for consumers, businesses and cities. Allego’s end-to-end charging solutions make it easier for businesses and cities to deliver the infrastructure drivers need, while the scalability of our solutions makes us the partner of the future. Founded in 2013, Allego is a leader in charging solutions, with an international charging network comprised of more than 26,000 charge points operational throughout Europe – and growing rapidly. Our charging solutions are connected to our proprietary platform, EV-Cloud, which gives us and our customers a full portfolio of features and services to meet and exceed market demands. We are committed to providing independent, reliable and safe charging solutions, agnostic of vehicle model or network affiliation. At Allego, we strive every day to make EV charging easier, more convenient and more enjoyable for all.

About Spartan Acquisition Corp. III

Spartan Acquisition Corp. III is a special purpose acquisition entity focused on the energy value-chain and was formed for the purpose of entering into a merger, amalgamation, capital stock exchange, asset acquisition, stock purchase, reorganization or similar business combination with one or more businesses. Spartan is sponsored by Spartan Acquisition Sponsor III LLC, which is owned by a private investment fund managed by an affiliate of Apollo Global Management, Inc. (NYSE: APO). For more information, please visit www.spartanspaciii.com.

Forward-Looking Statements.

This communication includes “forward-looking statements” within the meaning of the “safe harbor” provisions of the United States Private Securities Litigation Reform Act of 1995. These forward-looking statements are provided for illustrative purposes only and are not intended to serve as, and must not be relied on by any investor as, a guarantee, an assurance, a prediction or a definitive statement of fact or probability. Spartan Acquisition Corp. III’s (“Spartan”) and Allego Holding B.V.’s, a Dutch private limited liability company (“Allego”), actual results may differ from their expectations, estimates, and projections and, consequently, you should not rely on these forward-looking statements as predictions of future events. Words such as “expect,” “estimate,” “project,” “budget,” “forecast,” “anticipate,” “intend,” “plan,” “may,” “will,” “could,” “should,” “believes,” “predicts,” “potential,” “continue,” and similar

expressions (or the negative versions of such words or expressions) are intended to identify such forward-looking statements. These forward-looking statements include, without limitation, Spartan’s and Allego’s expectations with respect to future performance and anticipated financial impacts of the proposed business combination, the satisfaction or waiver of the closing conditions to the proposed business combination, and the timing of the completion of the proposed business combination.

These forward-looking statements involve significant risks and uncertainties that could cause the actual results to differ materially, and potentially adversely, from those expressed or implied in the forward-looking statements. Most of these factors are outside Spartan’s and Allego’s control and are difficult to predict. Factors that may cause such differences include, but are not limited to: (i) the occurrence of any event, change, or other circumstances that could give rise to the termination of the Business Combination Agreement and Plan of Reorganization (the “BCA”); (ii) the outcome of any legal proceedings that may be instituted against Athena Pubco B.V., a Dutch limited liability company (the “Athena Pubco”) and/or Allego following the announcement of the BCA and the transactions contemplated therein; (iii) the inability to complete the proposed business combination, including due to failure to obtain approval of the stockholders of Spartan, certain regulatory approvals, or the satisfaction of other conditions to closing in the BCA; (iv) the occurrence of any event, change, or other circumstance that could give rise to the termination of the BCA or could otherwise cause the transaction to fail to close; (v) the impact of the COVID-19 pandemic on Allego’s business and/or the ability of the parties to complete the proposed business combination; (vi) the inability to obtain or maintain the listing of Athena Pubco’s common shares on the New York Stock Exchange following the proposed business combination; (vii) the risk that the proposed business combination disrupts current plans and operations as a result of the announcement and consummation of the proposed business combination; (viii) the ability to recognize the anticipated benefits of the proposed business combination, which may be affected by, among other things, competition, the ability of Allego to grow and manage growth profitably, and to retain its key employees; (ix) costs related to the proposed business combination; (x) changes in applicable laws or regulations; and (xi) the possibility that Allego, Spartan or Athena Pubco may be adversely affected by other economic, business, and/or competitive factors. The foregoing list of factors is not exclusive. Additional information concerning certain of these and other risk factors is contained in Spartan’s most recent filings with the SEC and in the registration statement on Form F-4 (the “Form F-4”), including the proxy statement/prospectus forming a part thereof filed by Athena Pubco in connection with the proposed business combination on September 30, 2021. All subsequent written and oral forward-looking statements concerning Spartan, Allego or Athena Pubco, the transactions described herein or other matters and attributable to Spartan, Allego, Athena Pubco or any person acting on their behalf are expressly qualified in their entirety by the cautionary statements above. Readers are cautioned not to place undue reliance upon any forward-looking statements, which speak only as of the date made. Each of Spartan, Allego and Athena Pubco expressly disclaims any obligations or undertaking to release publicly any updates or revisions to any forward-looking statements contained herein to reflect any change in their expectations with respect thereto or any change in events, conditions, or circumstances on which any statement is based, except as required by law.

No Offer or Solicitation.

This communication is not a proxy statement or solicitation of a proxy, consent, or authorization with respect to any securities or in respect of the proposed business combination and shall not constitute an offer to sell or a solicitation of an offer to buy the securities of Spartan, Athena Pubco or Allego, nor shall there be any sale of any such securities in any state or jurisdiction in which such offer, solicitation, or sale would be unlawful prior to registration or qualification under the securities laws of such state or jurisdiction. No offer of securities shall be made except by means of a prospectus meeting the requirements of Section 10 of the Securities Act of 1933, as amended, or exemptions therefrom.

Important Information About the Proposed Business Combination and Where to Find It.

In connection with the proposed business combination, a registration statement on Form F-4 was filed by Athena Pubco with the SEC on September 30, 2021. Once declared effective, the Form F-4 will include a definitive proxy statement to be distributed to holders of Spartan’s common stock in connection with Spartan’s solicitation for proxies for the vote by Spartan’s stockholders in connection with the proposed business combination and other matters as described in the Form F-4, as well as a prospectus of Athena Pubco relating to the offer of the securities to be issued in connection with the completion of the business combination. Spartan, Allego and Athena Pubco urge investors, stockholders and other interested persons to read the Form F-4, including the proxy statement/prospectus incorporated by reference therein, as well as other documents filed with the SEC in connection with the proposed business combination, as these materials contain important information about Allego, Spartan, and the proposed business combination. Such persons can also read Spartan’s final prospectus dated February 8, 2021 (SEC File No. 333-252866), for a description of the security holdings of Spartan’s officers and directors and their respective interests as security holders in the consummation of the proposed business combination. After the Form F-4 has been filed and declared effective, the definitive proxy statement/prospectus will be mailed to Spartan’s stockholders as of a record date to be established for voting on the proposed business combination. Stockholders will also be able to obtain copies of such documents, without charge, once available, at the SEC’s website at www.sec.gov, or by directing a request to: Spartan Acquisition Corp. III, 9 West 57th Street, 43rd Floor, New York, NY 10019, or (212) 515-3200. These documents, once available, can also be obtained, without charge, at the SEC’s web site (http://www.sec.gov).

INVESTMENT IN ANY SECURITIES DESCRIBED HEREIN HAS NOT BEEN APPROVED OR DISAPPROVED BY THE SEC OR ANY OTHER REGULATORY AUTHORITY NOR HAS ANY AUTHORITY PASSED UPON OR ENDORSED THE MERITS OF THE OFFERING OR THE ACCURACY OR ADEQUACY OF THE INFORMATION CONTAINED HEREIN. ANY REPRESENTATION TO THE CONTRARY IS A CRIMINAL OFFENSE.

Participants in the Solicitation.

Spartan, Allego, Athena Pubco and their respective directors, executive officers and other members of their management and employees, under SEC rules, may be deemed to be participants in the solicitation of proxies of Spartan’s stockholders in connection with the proposed business combination. Investors and security holders may obtain more detailed information regarding the names, affiliations and interests of Spartan’s directors and executive officers in Spartan’s final prospectus dated February 8, 2021 (SEC File No. 333-252866), which was filed with the SEC on February 10, 2021. Information regarding the persons who may, under SEC rules, be deemed participants in the solicitation of proxies of Spartan’s stockholders in connection with the proposed business combination will be set forth in the proxy statement/prospectus for the proposed business combination when available. Information concerning the interests of Spartan’s, Athena Pubco’s and Allego’s participants in the solicitation, which may, in some cases, be different than those of Spartan’s, Athena Pubco’s and Allego’s equity holders generally, will be set forth in the proxy statement/prospectus relating to the proposed business combination when it becomes available.

Contacts

For Allego

Investors

investors@allego.eu

Media

allegoPR@icrinc.com

For Meridiam

FTI Consulting

meridiamsc@fticonsulting.com

For Spartan Acquisition Corp. III

Investors

info@spartanspacIII.com

Media

Communciations@apollo.com