MeV4He backscattering and x-ray diffraction analysis were used to examine the intermixing of niobium thin films on single crystal silicon during28Si+ion bombardment. The ambient temperature dependence of the intermixing is reported. The dependence cannot be explained by either radiation-enhanced diffusion or cascade mixing alone. The silicides. NbSi2and Nb5Si3, were both observed. Silicide growth was found to be proportional to the square root of the fluence for the case in which the ion range exceeds the film thickness.