Structure and physical properties of Cr5B3-type Ta5Si3 and Ta5Ge3

The Cr5B3-type Ta5Si3 phase was prepared by arc-melting, while the Cr5B3-type Ta5Ge3 one was synthesized through sintering at 1000 °C. X-ray single crystal diffraction was employed to elucidate their structure. According to the magnetization measurements, both Ta5Si3 and Ta5Ge3 are Pauli paramagnets, with Ta5Ge3 showing a Currie-Weiss-like paramagnetic behavior at low temperatures likely due to presence of paramagnetic impurity. Both Ta5Si3 and Ta5Ge3 display a very low electrical resistivity from 2 to 300 K. The resistivity is constant below 20 K, but displays a positive temperature coefficient above 20 K. Electronic structure calculations with the TB-LMTO-ASA method support the metallic character of the two phases and suggest that the bonding is optimized in both phases.