Polycrystalline Mn/Ga alloy thin films were grown by metal-organic chemical vapour deposition from the novel mixed metal single-source precursors (CO)(5)MnGaEt(2)(NR(3)) (NR(3)=N(CH3)(3), NC7H13) (1a-b) and [(CO)(5)Mn]Ga-2[(CH2)(3)NMe(2)] (2) on (111) silicon, (100) gallium arsenide and quartz slides. Perfect molecular control over the metal stoichiometry of the deposited mixed metal thin films was achieved. The films were examined by scanning electron microscopy with energy -dispersive X-ray analysis, Anger electron spectroscopy, and electrical conductivity measurements, and were characterized structurally by X-ray diffraction. The level of impurities (C, N, O) was found to be comparatively low, of the order of a few atomic per cent. The films exhibited a polycrystalline and polyphasic nature. Thin film reactions with the substrate material (silicon and GaAs) were observed above 300 degrees C.