Cubic Mn2Ga films with the half-Heusler C1(b) structure are grown on V (001) epitaxial films. The phase is a soft ferrimagnet, with Curie temperature T-C = 225K and magnetization M-s 280 kAm(-1), equivalent to 1.65 mu(B) per formula. Adding ruthenium leads to an increase of T-C up to 550 K in cubic Mn2RuxGa films with x = 0.33 and a collapse of the net magnetization. The anomalous Hall effect changes sign at x = 0.5, where the sign of the magnetization changes and the magnetic easy direction flips from in plane to perpendicular to the film. The Mn2Ru0.5Ga compound with a valence electron count of 21 is identified as a zero-moment ferrimagnet with high spin polarization, which shows evidence of half-metallicity.