Measurements of the magnetoresistance and Hall voltage have been made in the high-field region on the metallic fluorite compounds Au${\mathrm{Al}}_2$, Au${\mathrm{Ga}}_2$, and Au${\mathrm{In}}_2$. The results have been compared with those expected from the nearly-free-electron (NFE) model. These compounds are uncompensated. The magnetoresistance measurements in principal planes and directions, with one exception, support the NFE model, but the dimensions of the two-dimensional areas of aperiodic open orbits show pronounced deviations. Hall-effect measurements for B in the $〈100〉$ and $〈111〉$ directions indicate significant departures of the real Fermi surface from the NFE model. A proposed empirical model gives much better agreement with Hall-effect, magneto-resistance, and de Haas-van Alphen measurements. In the best Au${\mathrm{Ga}}_2$ crystal, magnetoresistance whiskers have been observed and classified in some detail. The magnetoresistance has been calculated for B in the {100} plane, assuming a constant relaxation time and a model of the fourth electron zone with a topography similar to the NFE Fermi surface.

• Received 29 October 1968

DOI:https://doi.org/10.1103/PhysRev.182.658