The transition from Schottky to ohmic contact in the nickel silicide/SiC system during annealing from 600 to 950 degreesC was investigated by measuring the electrical proprieties of the contact and by analyzing the microstructure of the silicide/SiC interface. After annealing at 950 degreesC the I-V characterisation shows the presence of a non uniform Schottky barrier with respect to the almost ideal diodes annealed at 600degreesC, which can be responsible for the rectifying-ohmic transition in the electrical behaviour.