Solid-phase reaction, Schottky barrier heights and contact resistivities at the interface of Ti/Si0.8Ge0.2/Si(100) systems have been investigated. At annealing temperatures below 300 degrees C, Ti atoms preferentially react with Si atoms. Ce atoms start to react with Ti above 400 degrees C and C54-Ti(Si1 - yGey)(2) with a fraction of y = 0.12 is formed by annealing at 650 degrees C. The annealing behavior of Schottky barrier heights suggests that the Ge composition of SiGe layers at the interface is Si-rich, which is consistent with the results on the interfacial reaction. For both n- and p-SiCe, the Schottky barrier heights lower than those of Ti/Si(100) are obtained at 650 degrees C, which is considered to be related to the reaction product such as C54-Ti(Si1 - yGey)(2). The contact resistivities smaller than those expected from the Schottky barrier heights are obtained for p(+)-SiGe at 580 degrees C. The sheet resistance of Ti/Si0.8Ge0.2/Si(100) and Ti/Ge(100) systems decreases at annealing temperatures above 550 degrees C and the values are as small as that of C54-TiSi2.