The coherence conundrum in BEDT-TTF superconductors; how does interlayer transport die as temperature rises?

Recent attention has focused on ``bad metals'', systems which appear to be Fermi liquids at low temperatures ($T)$, but whose conductivity falls below the minimum metallic limit as $T$ rises. A key question concerns the coherence of the electron orbitals, and whether, as suggested by Anderson and others, it is destroyed by thermal fluctuations as $T$ rises. To address this, we have studied magnetic-field-orientation-dependent transport in the organic superconductor (BEDT-TTF)$_{2}$Cu(NCS)$_{2}$ at temperatures of up to 45 K in magnetic fields of up to 45 T. This material was chosen because its Fermi surface (FS) is well characterized by experiment. We find that the angle-dependent magnetoresistance oscillations (AMROs) due to orbits on the quasi-one-dimensional (Q1D) and Q2D FS sections are suppressed by rising $T$, with a $T$ dependence suggesting phonon scattering. The coherence peak in the resistivity seen in exactly in-plane fields, and other signatures of a 3D FS, remain to values of $T$ that exceed the proposed Anderson criterion for incoherent transport by a factor of order 80! The implications of these data for currently-held ideas about bandstructure will be discussed.