MAGNETOTRANSPORT MEASUREMENT ON THE LAMBDA-PHASE OF THE ORGANIC CONDUCTORS (BETS)2MCL4 (M=GA, FE) - MAGNETIC-FIELD-RESTORED HIGHLY CONDUCTING STATE IN LAMBDA(BETS)2FECL4

Magnetotransport properties of two isostructural salts, the superconducting lambda-(BETS)2GaCl4 phase and the first organic conductor containing magnetic Fe3+ ions, lambda-(BETS)2FeCl4, where BETS is bis(ethylenedithio)tetraselenafulvalene, have been studied up to 37 T. The previously reported sharp metal-insulator phase transition occurring at 8 K under ambient pressure for lambda-(BETS)2FeCl4 is suppressed when applying magnetic fields > 10 T. This unusual phenomenon may be connected to a field-induced ferromagnetic ordering of the Fe3+-ions moments. This could result in some kind of ''decondensation'' of the carriers, initially condensed below 8 K, into a field-restored highly conducting state (FRHCS). The temperature-magnetic-field (T-H) phase diagram is presented. The angle dependence of the critical field H(c2) has been determined for the superconducting lambda-(BETS)2GaCl4 phase at 4.2 K.