Pulse magnetron sputtering was used to deposit Cr-5Si (at.%) thin layers onto CoSb 3 substrates to prevent degradation of the material at elevated temperatures. The quality of the protective layers was evaluated on the basis of oxidation tests in air at 500 and 600°C for up to 80 h. The surfaces, fractures and cross-sections of specimens were analyzed to assess integrity and adherence of the deposited layer as well as the extent of reaction and diffusion phenomena at interfaces. It was found that the Cr-5Si layer provided a satisfactory protection for CoSb 3 at 500°C. Promising results were obtained at 600°C.