Flux jumps and melting of the vortex lattice in κ-(ET)2Cu(NCS)2

The angular and temperature dependence of the DC magnetization of the organic superconductor κ-(ET) 2 Cu(NCS) 2 has been investigated in high magnetic fields (up to 20 T) and at low temperatures (25-200 mK). In moderate fields, the mixed state of this layered superconductor exhibits a series of flux jumps, indicative of critical surface screening currents. At higher fields, a melting of the quasi-two-dimensional vortex lattice is observed below the irreversibility line.