Superconductivity in ScGa$_3$ and LuGa$_3$

We are reporting low-temperature superconductivity in single crystals of ScGa$_3$ and LuGa$_3$. While the latter compound had been listed as a superconductor before, superconductivity in the former compound had never been observed, and characterization of the low-temperature state was lacking in both compounds. By measurements of magnetization, specific heat and resistivity, we show that RGa$_3$ (R = Sc and Lu) are conventional BCS superconductors with T$_c$ around 2.3 K and the upper critical field less than 240 Oe. The experimental results agree with band structure calculation estimate of the critical temperature.