Thermal conductivity of organic superconductors in oriented magnetic field

We report study of thermal conductivity of organic superconductors in magnetic field of varying orientation with respect to the conducting plane, paying special attention to the parallel case. At low temperatures the field dependence of thermal conductivity in this configuration shows notable difference from usual behavior, both for electronic and phononic contributions. We show that the behavior of the electronic thermal conductivity in organic superconductor λ-(BETS) 2 GaCl 4 is consistent with the formation of an inhomogeneous Fulde-Ferrel-Larkin-Ovchinnikov superconducting state. In a closely related antiferromagnetic superconductor κ-(BETS) 2 FeBr 4 interaction with magnetic sublattice leads to a first order transition at H c2 in parallel magnetic field and reentrant superconductivity at high fields. The phonon thermal conductivity is shown to be a good tool for picking up a dimensional crossover and lock-in transition in the vortex system.