  The nature of the low-temperature phase of the quasi-two-dimensional
conductors $\alpha-(BEDT-TTF)_2{M}Hg(SCN)_4$[{M}=K,Rb,Tl] is considered. It is
argued that the magnetic field dependence of the phase diagram is more
consistent with a charge-density wave, rather than a spin-density wave ground
state. The phase diagram of a charge-density wave in a magnetic field is
discussed using a Ginzburg-Landau free energy derived from microscopic theory.
New experiments are proposed to test the charge-density-wave hypothesis and
detect an additional high field phase.
