MICROWAVE SURFACE IMPEDANCE OF KAPPA-(BEDT-TTF)2CU(NCS)2, WHERE BEDT-TTF IS BIS(ETHYLENEDITHIO)TETRATHIAFULVALENE - EVIDENCE FOR UNCONVENTIONAL SUPERCONDUCTIVITY

High-sensitivity microwave-impedance measurements performed on the quasi-two-dimensional organic superconductor kappa-(BEDT-TTF)2Cu(NCS)2 give sound evidence for an unconventional type of superconductivity. The penetration depth lambda(T) is in excellent agreement with recent muon-spin-relaxation measurements which are consistent with anisotropic pairings with lines of nodes in the energy pp. The real part of the conductivity sigma1 shows a peaked structure which is free of coherence factor effects and results from a competition between two temperature dependences, the penetration depth and the inelastic relaxation time of the normal fluid.