Magnetoresistance of layered conductors under conditions of topological   phase transition
  The resistance of layered conductors with a multisheet Fermi surface (FS), in a high magnetic field, in the immediate vicinity of Lifshic's topological transition when the separate FS sheets are drown together by an external action, pressure in part (and eventual change of the FS connectivity) is studied theoretically. Analysis of magnetoresistance near topological transition is illustrated for the case of FS in the shape of lightly corrugated cylinder and two corrugated planes distributed with a repeated period in the pulse space. It yields, that as the FS plane sheets approach sufficiently the cylinder, the charge carriers produce a magnetic breakdown of one FS sheet to another, decreasing a sharp anisotropy of magnetoresistance to the in-plane current. Instead of square increase with a magnetic field, the slower resistance growth remains linear in the field within a broad magnetic-field range. In the intimate vicinity of topological transition, when the energy gap between FS layers is negligibly small, the resistance is saturated. 
O. Galbova, V. Peschansky
cond-mat.mes-hall