Anion gap and stability of the metallic phase for (TMTSF)₂ClO₄

Starting with the prototype nesting spectrum of (TMTSF)₂PF₆, it is emphasized that the gap due to anion ordering (AO) would result in a somewhat different SDW state for ClO₄ if the "antinesting" term, t′_b, was omitted. The field then first diminishes that term, improving nesting. At the same time the field decreases pairing between subbands with nesting features because of the difference in the symmetry of their wavefunction. This leads to the reentrance of the metallic state. The magnetic breakdown (M B) gradually decreases the effect of AO. Properties of the "prototype" PF₆-material are expected to be seen again at large magnetic fields. However, it occurs in a peculiar phase diagram with sharp spikes in T_SDW periodic in the inverse magnetic field, 1/H. Cyclotron resonance on open orbits is discussed to study whether the "transverse" gap due to AO in (TMTSF)₂ClO₄ manifests itself in other properties.