EFFECTIVE ELECTRONS AND ANGULAR OSCILLATIONS IN QUASI-ONE-DIMENSIONALCONDUCTORS

We show via calculation and experiment that a recently observed angula r magnetoresistance effect in low-dimensional conductors can be explai ned by ''effective electrons,'' which dominate the conductivity for ma gnetic-held orientations near inflection points on a warped Fermi surf ace. Closed orbits, which form in certain field orientations, play an insignificant role. In studies of the quasi-one-dimensional molecular metal (TMTSF)(2)PF6, we observe, in addition to sharp kink structure o f the effect, a series of strong angular oscillations that we ascribe to the Lebed' commensurability resonance (magic angle) effect.