MAGNETORESISTANCE OF KAPPA-(BEDT-TTF)(2)X IN NORMAL AND MIXED STATES

The interlayer magnetoresistance (MR) of kappa-(BEDT-TTF)(2)X supercon ductors with X=Cu(NCS)(2) and Cu[N(CN)(2)]Br in fields both above and below H-c2 has been studied. In the former salt, nearly temperature in dependent oscillations originating from the quantum interference in th e magnetic breakdown regime have been directly observed above 2 K in f ields 12-14 T. In coIltrast to the three-dimensional (3D) case, the ef fect survives at tilting the field from the crystallographic symmetry direction up to the angles as high as 40 degrees. In the other salt cl ear MB oscillations corresponding to 100% of the Brillouin zone cross- section area have been found above 22 T. Below H-c2, the interlayer re sistance is shown to be almost independent of the field direction in a wide angle range around the parallel-to-plane orientation. This resul t is believed to reflect the strongly two-dimensional nature of the vo rtex state in the title compounds.