LEBEDS MAGIC ANGLE EFFECTS IN (TMTSF)2PF6

Lebed predicted striking effects in both the metallic and field-induced spin-density-wave (FISDW) states of quasi-one-dimensional conductors when the orientation of the magnetic field causes commensurate electron motion in the least-conducting plane. We have observed sharp cusplike dips in the normal-state magnetoresistance of (TMTSF)2PF6 suggesting a giant resonance at the commensurate angles. On entering the FISDW state some of the dips become peaks, others fade, and fractional states appear. Magic angle effects are also prominent in the phase boundary of the FISDW state and in the Hall resistance.