The contact reaction between a silicon substrate and codeposited Ir-V alloy films of composition IrxV100-x where x is 25, 50 or 80 were studied. Interdiffusion and compound formation were analysed by Auger electron spectroscopy and X-ray diffraction. The expected formation of IrSi and Ir2Si3 at relatively low temperatures is prevented by the formation of stable Ir-V intermetallic compounds. Silicide formation is observed only after anneals at about 700°C, when VSi2, Ir2Si3 and tracks of IrSi are detected. This is accompanied by component redistribution in the thin films, the details of which depend on the alloy composition.