[1] Mathis was in charge of the library of humanities and social science at the Paris Descartes University from 2008 to 2010.

Since 2010, he has been a curator for 17th century collections at the Department of Prints and Photographs of the National Library of France.

He is the editor of the French academic journal on printmaking Nouvelles de l'estampe.

His dissertation, written under the supervision of Lucien Bély and Olivier Poncet, focuses on Simon Arnauld de Pomponne.

[8] In April 2013, the French interior intelligence agency Direction centrale du renseignement intérieur (DCRI) pressured Mathis into deleting the French language Wikipedia article about the Pierre-sur-Haute military radio station, under threat of detention and criminal charges.