Low temperature properties of calcium mono- and disilicides

Low temperature electronic and lattice properties of polycrystalline CaSi and CaSi, have been studied by means of specific heat, resistivity, Hall effect and magnetoresistance measurements. Although these metals have comparable density of electronic states at the Fermi level (0.42 states/eV atom and 0.19 states/eV atom for CaSi and CaSi2 respectively) the resistivity of CaSi2 (rho(273) (K)=33.2 mu Omega cm) is almost one order of magnitude lower than that of CaSi (rho(273) (K) = 282 mu Omega cm). The analysis of magnetotransport properties suggests that both these materials are compensated metals and the estimated density of carriers is one order of magnitude higher for CaSi, than for CaSi. In agreement with electronic band structure calculations we concluded that electrons of the Ca d-band play a dominant role for the charge transport. The Debye temperature estimated from different experiments is higher for CaSi2 than for CaSi and this confirms that the Ca-Si interaction increases as the Si concentration increases. (C) 1998 Elsevier Science S.A.