EFFECT OF PRESSURE ON TRANSPORT-PROPERTIES OF NI(S1-XSEX)(2)

Resistivity and Hall effect measurements were made on single crystals of NiS2 and Ni(S0.9Se0.1)(2) under high pressure in a temperature rang e between 4.2 and 300 K. NiS2 and Ni(S0.9Se0.1)(2) show insulator-meta l transitions. Anomalous behavior of resistivity corresponding to a pa ra-antiferromagnetic transition was found in the metallic phase. The H all coefficient and the Hall mobility decrease with increasing pressur e. It is suggested that the electronic structure of Ni(S1-xSex)(2) in the insulating phase is modified toward the phase boundary of the insu lator-metal transition.