Magnetoconductivity of a metal with a closed Fermi surface reconstructed by a biaxial density wave

We investigate quantum dynamics and kinetics of a 2D conductor with a closed Fermi surface reconstructed by a biaxial density wave, in which electrons move along a two-dimensional periodic net of semiclassical trajectories coupled by the magnetic breakdown tunneling under a strong magnetic field. We derive a quasiparticle dispersion law and magnetoconductivity tensor. The quasiparticle spectrum is found to be the alternating series of two-dimensional magnetic energy bands with gaps between them. The longitudinal magnetoconductivity shows giant oscillations with change of magnetic field, while the Hall coefficient changes sign and is absent in a wide range of the magnetic fields in between. Preliminary estimations show that the suggested magnetoconductivity mechanism may be the origin of such behavior of the Hall coefficient versus magnetic field, as observed in experiments in materials with analogous topology of the Fermi surface, such as the high-Tc supercondu