Interfacial reactions, phase formation, microstructure, and composition, as functions of heat treatments (400–800 °C) were investigated in Ni90Ti10alloy thin film coevaporated on ann‐type 6H‐SiC (0001) single‐crystal substrate. The study was carried out with the aid of Auger electron spectroscopy, x‐ray diffraction, and analytical transmission electron microscopy. The interaction was found to begin at 450 °C. Ni and C are the dominant diffusing species. The reaction zone is divided into three layers. In the first layer, adjacent to the SiC substrate, the presence of Ni‐rich silicide, Ni2Si, and C precipitates, was observed. The second layer is composed mainly of TiC, while the third consists of Ni2Si. This composite structure, consisting of the silicide as a low resistivity ohmic contact, and of the carbide as a diffusion barrier, promises high‐temperature stability crucial to ohmic contact development for SiC technology. Factors controlling phase formation in the Ni–Ti/SiC system are discussed. ©1996 American Institute of Physics.