HALL-EFFECT IN THE MIXED-STATE OF THE ORGANIC SUPERCONDUCTOR KAPPA-(BEDT-TTF)(2)CU(NCS)(2)

We report on the Hall effect measurements of the quasi two-dimensional organic superconductor kappa-(BEDT-TTF)2Cu(NCS)2. A sign reversal phe nomenon of the Hall resistivity is found in the mixed state. The Hall conductivity changes monotonically with field and temperature in contr ast to the peak structure observed in the Hall resistivity. In low fie lds, the Hall conductivity diverges to infinity as -1/(H - H), where H is characteristic field in which the resistivity becomes zero. The phase diagram is proposed from these results.