Resistivity studies on the layered semi-metallic CaAl2Si2: evaluating its temperature-, field- and...

We studied the layered, hexagonal, semi-metal CaAl(2)Si(2) by magnetization, specific heat and resistivity measurements over a wide range of temperature, pressure and magnetic field. Both the Sommerfeld coefficient (γ = 1 mJ mol(-1) K(-2)) and the Debye temperature (θ(D) = 288 K) are in agreement with the values obtained from the band structure calculation. The resistivity shows a metallic character up to 200 K, followed by saturation and, afterwards, a weak decrease up to 840 K, at which it sharply rises reaching a local maximum at 847 ± 5 K. While the low-temperature thermal evolution was accounted for in terms of intrinsic and extrinsic effects, the additional high-temperature scattering was attributed, based on differential thermal analysis, to a first-order thermal event. No appreciable magnetoresistivity was observed at liquid helium temperatures even for fields up to 90 kOe, indicating an absence of coupling between the electronic and magnetic degrees of freedom. Finally, an externally applied pressure was found to induce a strong reduction in the resistivity following a second-order polynomial: this effect will be discussed in terms of the influence of pressure on the effective mobility and concentration of charge carriers.