Seebeck and Nernst effects in the mixed state of κ-(BEDT-TTF)2Cu(NCS)2

A comparative study of the Seebeck and Nernst effects in the mixed state of the organic superconductor κ-(BEDTTTF)2Cu(NCS)2 is reported. The Seebeck effect data can be explained well by an extended two-fluid counterflow picture proposed by Huebener et al. Anomalous behavior of the Seebeck effect reported so far is not intrinsic but results from the artificial misalignment of the sample. From the Nernst effect data, the transport entropy of magnetic-flux lines is obtained. This value agrees with that obtained from another way of the Seebeck effect measurements. Due to the pronounced fluctuation effect around Tc(H), there is a finite value of the transport entropy at T > Tc(H).