Electron transport and magnetic properties of semimetallic LuAs

Polycrystalline samples of LuAs with a residual resistivity ratio (RRR) between 2.52 and 3.38 were examined by: X-ray diffraction, magnetisation, resistivity, magnetoresistivity, Hall coefficient and thermoelectric power S(T), in addition to the nuclear magnetic resonance (NMR) of 75As and 175Lu nuclei. The density and mobility of carriers for the valence and conduction bands were determined for the RRR = 2.52 sample and used for the calculation of thermoelectric power, Sc(T). The value of Sc(T) fits well with that determined by experiment. The sample shows a charge imbalance with the number of electrons n, (holes, p) equal to 1.52 × 1020 (1.12 × 1020) e/cm3 at 4 K. This imbalance decreases with temperature, reversing after passing a minimum at ∼80 K and then increasing to n (p) = 9.4 × 1019 (1.42 × 1020) e/cm3 at 300 K. The 75As NMR Knight shift is found to be temperature independent and equal to 0.102% and the 175Lu NMR resonance frequency is shifted to higher values by ca. 0.011% with respect to that of LuSb. All data indicate that LuAs belongs to semimetals and the clearly observed 175Lu NMR multiquadrupolar echoes suggest the existence of defects in the cubic structure of the investigated samples.