We have performed detailed studies of the angle-and temperature-dependent resistive upper critical fields in the layered organic superconductor κ-(BEDT-TTF) 2 Cu(NCS) 2 . With the magnetic field lying in the conducting planes, our measurements show an upper critical field which comfortably exceeds the Pauli-paramagnetic limit in this material. We find no azimuthal angle dependence of the critical field, in spite of recent evidence that this material has gap nodes characteristic of d-wave superconductivity. We propose that the large critical fields may be due to a Fulde-Ferrell-Larkin-Ovchinnikov state which can exist in exactly in-plane fields because of the nature of the Fermi surface of κ-(BEDT-TTF) 2 Cu(NCS) 2 .

Field Suppression of the Heavy-Fermion State in Ceru2si2Vandermeulen, H.P.; Devisser, A.; Franse, J.J.M.; Berendschot, Ttjm; Perenboom, Jaaj; Vankempen, H.; Lacerda, A.; Lejay, P.; Flouquet, J.

Experimental evidence is presented for the appearance of new plateaux in the di.fferential conductance of a ballistic ID channel in the high DC bias regime. In zero magnetic field, we observe steps in the differential conduction of e2/h, as opposed to the conventional value of 2e2/h for a spin-degenerate ID subband. The new plateaux are found to be at quantised values to an accuracy of a few per cent and are described well by a model that assumes the bias is dropped symmetrically in the ID channel. In addition, all the plateaux disappear with increasing DCvOhge bias which can be explained in terms of an enhancement of the tunnelling probability. The same effects persist in a transverse magnetic field and we are able to calculate subband spacings as a function of the applied magnetic field.

Electronic properties of UNiAl in high magnetic fieldsBruck, E.H.; Nakotte, H.; de Boer, F.R.; de Chatel, P.

We repon angle-dependent magnetoresistance experiments on the charge-transfer salt cr-ET2KHgW.S)r using fields of up to 30 T. The data indicale tJnI the widely reported high-field 'kink' observed in the magnetoresistance of Ute a-ET$Wig(NCS)4 (M = K, TI, Rb) family of charge-bansfer salts represents a transition from an imperfectly nested spin-density wave gmund state, characterired by a quasi-onedimensional Fermi surface sheet tilted with re~peet to Ihe b'c plane, to a state with a cylindrical two-dimensional Fermi surface. Charge-transfer salts of the molecule ET (bis(ethy1enedithio)tetrathiafulvalene or BEDT