Thermal conductivity and thermoelectric power of CuIr2S4 and CuIr2Se4 spinels

The thermal conductivity and thermoelectric power against temperature over the range 10-300 K were measured for thiospinel CuIr2S4 and selenospinel Cu Ir2Se4. Sharp jumps with hystereses are observed in both the thermal conduc tivity and the thermoelectric power of CuIr2S4 as functions of temperature. The jumps at about 230 K are caused by the metal-insulator phase transitio n related to a change in structure from cubic to tetragonal with a temperat ure decrease. The results are interpreted in terms of the standard theories in which the transition is taken for granted. No such behaviour of these t ransport coefficients is observed in metallic CuIr2Se4.