Substitution effect on the superconductivity in W_5-xTa _xSiB₂ with the T₂ phase structure

We report here the magnetic susceptibility and electrical resistivity measurements of W5-xTaxSiB2. W5-xTaxSiB2 crystallizes in a tetragonal (the Mo5SiB2 (T2 phase) type) structure. We evaluated the effect of the partial substitution of Ta in W5SiB2. The superconductivity was observed below x 2 in W5-xTaxSiB2. As substituted Ta for W, the superconducting transition temperature (Tc) clearly enhanced from 5.8 K to 6.5 K. The largest volume fraction exhibits at x 0.2 sample. Thus, this work shows, for the first time, the superconductivity in W5-xTaxSiB2. Moreover, we determined that the dominant carrier sign of W5SiB2 are the hole from the thermoelectric power measurement and discussed about the enhancement of Tc of W5-xTaxSiB2 system.