Metal-phase stability of (TMTSF)2ClO4 in high magnetic fields, where TMTSF is tetramethyltetraselenafulvalene

The field-induced spin-density-wave state in (TMTSF)₂ClO₄, where TMTSF is tetramethyltetraselenafulvalene, develops because the field diminishes the ``antinesting'' terms, t'<sub>b</sub>, to restore the spin-density wave (SDW) that would exist at t'<sub>b</sub>=0 despite the anion gap in ClO<sub>4</sub>. The gap changes the wave function's symmetry for ``nested'' subbands-one of them changes sign upon crossing the new zone boundary, destroying the coherence of paired electrons at H≠0. Competition between the two phenomena leads to a reentrance of the metallic state. Magnetic breakdown is unable to restore a PF₆-type ground state and reveals itself in a pattern of peaks for T_SDW(H) periodic in H^-1.