Incoherentversuscoherent interlayer transport in layered conductors under a magnetic field

Comparative studies of the interlayer magnetoresistance of the layered organic conductor alpha-(BEDT-TTF)(2)KHg(SCN)(4) as a function of the magnetic field orientation have been performed oil different samples.The results obtained on the high quality crystal reveal a well defined three-dimensional Fermi surface and provide an evaluation of the interlayer transfer integral, t(perpendicular to) congruent to 0.04 meV. The lower quality crystal exhibits a very different behavior which is most likely caused by the breakdown of the three-dimensional coherence, when the scattering rate tau(-1) exceeds the interlayer hopping rate similar to t(perpendicular to)/h.