Crystal growth, low-temperature specific heat, and electronic structure of the filled skutterudite compound ThOs4As12

Single crystals of the filled skutterudite compound ThOsAs were grown by a Cd:As flux method. Low-temperature specific-heat measurement reveals a very small Sommerfeld coefficient of the electronic term mJ/molK, indicative of a semiconducting or semimetallic character of ThOsAs. A low electronic density of states at the Fermi level is consistent with anticipations based on the Zintl concept for the filled skutterudites as well as with our results of band structure calculations. Investigations of a nonmagnetic material ThOsAs can be relevant to unmask puzzling strong electron correlations in the putative topological Kondo insulator CeOsAs.