Hole theory and Quantum Electrodynamics in an unknown French manuscript by Ettore Majorana

We give an accurate historical and scientific account of a previously unknown manuscript written by Ettore Majorana in French. The retrieved text deals with Quantum Electrodynamics by using the formalism of field quantization, and it is here reported, for the first time, in translation. It is likely related to an invited talk for a conference at Leningrad (or Kharkov) in 1933 (or 1934) which, however, Majorana never attended. Probably this manuscript refers to the last missing papers of the ``Senatore folder'', given by Majorana to one student of his at the University of Naples in 1938, just before his disappearance.