Reentrant meissner effect in the organic superconductor /spl kappa/-ET/sub 2/CU[N(CN)sub 2/Cl/sub 1-x/Br/sub x/ under pressure

Summary form only given. Metallic conductivity and superconductivity (SC) in the title compound is only observed under hydrostatic pressure [1]. The critical pressure for the occurrence of SC (/sub Pcritical/=290bar for x=0) is lowered with increasing Br-content. In a pressure range above this pressure, whose width seems to depend on sample quality, reentrant SC is observed [2], presumably due to a competition with a magnetic ground state. We show by means of DC diamagnetic measurements, that the reentrant SC is a volume property and that the reentrant transition is a first order transition from a superconducting to a highly resistive and magnetically ordered state.