Magnetoresistance and magnetic breakdown in the quasi-two-dimensional conductors (BEDT-TTF)(2)MHg(SCN)(4)[M=K,Rb,Tl]

The magnetic-field dependence of the resistance of~BEDT-TTF! 2MHg~SCN!4@M5K,Rb,Tl# in the densitywave phase is explained in terms of a simple model involving magnetic breakdown and a reconstructed Fermi surface. The theory is compared to measurements in pulsed magnetic fields up to 51 T. The value implied for the scattering time is consistent with independent determinations. The energy gap associated with the densitywave phase is deduced from the magnetic breakdown field. Our results have important implications for the phase diagram. @S0163-1829~96!52036-9#