  Detailed studies of the magnetoresistance of alpha-(ET)2KHg(SCN)4 and
alpha-(ET)2TlHg(SCN)4 as a function of temperature, magnetic field strength,
and field orientation are reported. Below 15 K, the temperature dependence of
the magnetoresistance is metallic (dR/dT > 0) for magnetic field orientation
corresponding to an angular dependent magnetoresistance oscillation (AMRO)
minimum and nonmetallic (dR/dT < 0) at all other field orientations. We find
that this behavior can be explained in terms of semiclassical models without
the use of a non-Fermi liquid description. The alternating temperature
dependence (metallic/nonmetallic)with respect to field orientation is common to
any system with either quasi-one or two-dimensional AMRO. Furthermore, we
report a new metallic property of the high field and low temperature regime of
alpha-(ET)2MHg(SCN)4 (where M = K, Rb, or Tl) compounds.
