Order parameter of the metal to insulator phase transition in the thio spinel CuIr2S4

The temperature dependences of the resistivity, the magnetoresistance and the Hall effect of the Mott compound CuIr2S4-y have been measured through the metal insulator transition temperature T-mi, in the temperature range 4.2 K<T<300 K and in magnetic fields up to 5 Tesla, We observed carrier concentrations of 10(20) cm(-3) in the insulating and of 10(22) cm(-3) in the metallic state. Anomalies in the resistivity curve rho(T), an anomalous shift of T-mi in magnetic fields, dT(mi)/dH= +0.3 K/T, and a structure of the magnetoresistance to T-mi were observed and interpreted in terms of quasi-particle formation. (C) 1998 Published by Elsevier Science S.A.