X-ray diffraction, scanning electron microscopy, and Auger electron spectroscopy were used to study the phase formation and kinetics of interfacial reactions in the a-SiSi1-xGex:H/Cr/quartz system after heating to 300-800°C by rapid thermal annealings or vacuum annealings for 10s-12h. We used amorphous Si1-xGex films of various compositions: x = 0, 0.3, 0.8, and 1.0 deposited by glow discharge over Cr-covered fused quartz substrates. No reaction between Cr and SiGe:H in the system was detected up to 400°C. We found that the Ge-rich films were more reactive with the Cr underlayer than the Si-rich films. The main reaction product of the SiGe and Cr interaction was Cr4Ge3.