LEBED RESONANCE EFFECTS IN THE METALLIC AND SPIN-DENSITY-WAVE PHASES OF (TMTSF)2PF6

The angular dependence of the magnetoresistance along the least conduc ting axis has been investigated in both metallic and field-induced spi n-density-wave (FISDW) states of the quasi-one-dimensional organic con ductor (TMTSF)2PF6. Strong dips in the resistance occur for Lebed's << magic>> field orientations associated to resonant effects in the open- orbit electron motion. The dips exist in both the metallic and the FIS DW states but gradually fade away with increasing field in the latter state. The study of the FISDW phase transitions as a function of field orientation confirms the existence of a minimum for the threshold fie ld in the vicinity of a magic angle. Such an anomaly is not observed i n the angular dependence of successive transition fields within the FI SDW state.