Heat Conduction in $\kappa$-(BEDT-TTF)${}_2$Cu(NCS)${}_2$

The first study of thermal conductivity, $\kappa$, in a quasi-two-dimensional organic superconductor of the $\kappa$-(BEDT-TTF)${}_2$X family reveals features analogous to those already observed in the cuprates. The onset of superconductivity is associated with a sudden increase in $\kappa$ which can be suppressed by the application of a moderate magnetic field. At low temperatures, a finite linear term - due to a residual electronic contribution- was resolved. The magnitude of this term is close to what is predicted by the theory of transport in unconventional superconductors.