ynthesis and superconducting proprieties on the Nb-Co-B system

Since the discovery of the superconductivity in MgB$_{\mathrm{2}}$ a renew interest in borides systems have increased in the last years. The interesting in the boride systems is how rare is the superconductivity occurrence. Many MRB$_{\mathrm{2}}$ (MR - Refractory metal) crystallize in the same prototype structure than MgB$_{\mathrm{2}}$ type AlB$_{\mathrm{2}}$. However just NbB$_{\mathrm{2}}$ is a known superconductor material with superconducting critical temperature close to 3.9 K. So in this work we shall show results which suggest that small substitution of Nb for Co on the Nb$_{\mathrm{1-x}}$Co$_{\mathrm{x}}$B$_{\mathrm{2}}$ stoichiometry nominal increase superconducting critical temperature from 3.9 K without Co to 5 K in the Nb$_{\mathrm{0.95}}$Co$_{\mathrm{0.05}}$B$_{\mathrm{2}}$ nominal composition. These results are sustained by magnetization, resistivity and heat capacity measurements.