Superconductivity in the T$_{2}$ phase of the Ta-Ge-B system

In the Ta-Ge system the $\alpha$Ta$_{5}$Ge$_{3}$ phase is not superconductor. Considering the high solubility of this phase for boron, in this work it has been evaluated the effect of boron doping in $\alpha$Ta$_{5}$Ge$_{3}$ on the electrical, heat capacity and magnetic properties of the produced materials. It has been shown that boron doping promoted superconductivity for some specific composition. The Ta$_{5}$GeB$_{2}$, also named T$_{2}$ phase, crystallizes in the tetragonal symmetry with Cr$_{5}$B$_{3}$ prototype structure. In this composition the sample presented the maximum superconducting critical temperature (3.4 K). Others systems that exhibit the existence of the T$_{2}$ phase present superconductivity such as Mo$_{5}$SiB$_{2}$ (T$_{c}$ $\sim$5.5 K), Nb$_{5}$Si$_{3-x}$B$_{x}$ (T$_{cmax}$ $\sim$7.8 K) and W$_{5}$SiB$_{2}$ (T$_{c}$ $\sim$5.5 K). Thus, Ta$_{5}$GeB$_{2}$ is more one example.