MAGNETIZATION AND H-C2 OF A KAPPA-(BEDT-TTF)(2)CU[N(CN)(2)]BR SINGLE-CRYSTAL

The magnetization curves of the organic superconductor kappa(BEDT-TTF) (2)Cu[N(CN)(2)]Br have been measured in fields up to 200 kOe and tempe ratures down to 0.4 K. Above the irreversibility field, which is found finite in the limit T-->0, the curves can be rescaled according to th e two-dimensional fluctuation theory in a high magnetic field. However , the mean field upper critical field found in this way exhibits an up turn below T approximate to 5 K which is not likely due to a dimension al crossover. We suggest that a diamagnetic contribution to the magnet ization, in addition to the thermal fluctuations one, could be at the origin of the effect.