Sputtering yields of Si and Ni from thin layer films of Ni-Si compounds (Ni sub(1-x)Si sub(x)), including the pure materials (Ni and Si), caused by 5keV Ar/sup +/ ion bombardment were investigated using backscattering spectrometry. The sputtering yield for Si from Ni sub(1-x)Si sub(x) increased with increasing Si concentration. However, there is an abrupt decrease in the yield for Si concentrations above NiSi/sub 2/ to pure Si. This is in clear contrast to the sputtering yield of Ni from Ni sub(1-x)Si sub(x) which increased with increasing Ni concentration monotonously. These results are discussed on the basis of both the difference in the atomic density and the electronic state of the alloy.