Specific heat of Sb: Isotopic and spin-orbit effects from measurements and ab initio calculations

We report measurements of the specific heat C of antimony crystals in the 2-50 K temperature range for several isotopic compositions and ab initio calculations of the specific heat as a function of temperature. The contribution of spin-orbit interaction and the dependence of C on isotopic mass are discussed and compared with previous observations reported for semiconductors and group VA semimetals. We also discuss the effect of spin-orbit interaction on the trigonal lattice parameter and the cohesive energy.