The metallic (high-pressure) phase of ${\mathrm{}\left(\mathrm{TMTSF}\right)\mathrm{}}_2$P${\mathrm{F}}_6$ exhibits Shubnikov—de Haas resistance variations at low temperatures. A single frequency of 0.76 MG has been recorded. A large anisotropy in the transverse magnetoresistance is also observed. Our results imply a two-dimensional Fermi surface under pressure, with compensated electron and hole sections oriented along the crystal $c$ axis. Some unusual and physically significant anomalies associated with the oscillations are discussed.

• Received 9 February 1981

DOI:https://doi.org/10.1103/PhysRevLett.46.1296