SPECIFIC-HEAT OF SUPERCONDUCTING KAPPA-(BEDT-TTF)2CU(NCS)2 NEAR TC [WHERE BEDT-TTF IS BIS(ETHYLENEDITHIO)TETRATHIAFULVALENE]

High-resolution specific-heat measurements on a small (0.2 mg) single crystal of -(BEDT-TTF)2Cu(NCS)2 in magnetic fields up to 5 T reveal a jump C at Tc. Comparison with =34 mJ/mol K2 derived from Pauli paramagnetism yields C/Tc=1.500.15, within experimental error of the BCS value of 1.43. Application of a magnetic field broadens the transition but depresses it only slightly: -Hc2=16 T/K for H parallel to the planes, 0.75 T/K perpendicular. These very large values are, respectively, factors of 7 and 4 times higher than reported from magnetoresistance data, suggesting that flux-flow resistance obscures Tc in magnetoresistance measurements, much as it does in the ceramic high-Tc materials. No evidence is found for the presence of an anomaly near 4 K, as observed in proton NMR relaxation rates. © 1990 The American Physical Society.