  Superconductivity with $T_{\rm c}$ $\simeq$ 2 K was discovered in the
intermetallic binary compounds Rh$_2$Ga$_9$ and Ir$_2$Ga$_9$. This is the first
observation of superconductivity in the Rh-Ga and Ir-Ga binary systems. Both
compounds crystallize in a distorted Co$_2$Al$_9$-type structure (monoclinic,
space group: $Pc$), which lacks spatial inversion symmetry. Specific heat
measurements revealed that both compounds are weak-coupling BCS superconductors
having an isotropic superconducting gap. Measurements in magnetic fields
indicated type-I superconductivity with a critical field $H_{\rm c}(0)$
$\simeq$ 130 Oe for Rh$_2$Ga$_9$ and type-II superconductivity with an upper
critical field $H_{\rm c2}(0)$ $\simeq$ 250 Oe for Ir$_2$Ga$_9$.
