The first epitaxial platinum gallium two (PtGa2) films have been grown on gallium arsenide (GaAs) (100) by co-evaporation of the elements under ultra-high vacuum conditions. An electron beam evaporator and a Knudsen cell were used to produce the platinum and gallium beams, respectively. The resulting films and bulk PtGa2 have been characterized by x-ray diffraction, Auger electron spectroscopy, and x-ray photoelectron spectroscopy. The data confirm the PtGa2 stoichiometry and crystal structure of the films, and demonstrate their chemical stability on GaAs (100). This study supports the contention that PtGa2 can be a suitable, temperature stable contact material on GaAs substrates.