Heat conduction in κ-(BEDT-TTF)2X superconductors

We present the first study of thermal conductivity of a quasi two dimensional organic superconductor. κ-(BEDT-TTF) 2 Cu(NCS) 2 presents features which have already been detected in the high T c cuprates. Notably we observed an increase of the thermal conductivity at the superconducting transition which is suppressed by a moderate magnetic field. At low temperatures we clearly resolved a residual electronic contribution close to the universal limit value which is consistent with an anisotropic pairings with lines of nodes in the superconducting gap function.