  We examined the physical properties of homologous LanRu3n-1B2n (n = 1 - 3)
series including a new compound of n = 2. All of these compounds showed strong
electron-electron correlation characterized by large Wilson ratio. In contrast
to LaRu2B2 and La2Ru5B4 that show normal metal behaviors down to 1.8 K, we
discover La3Ru8B6 is an intermediately coupled BCS superconductor with Tc ~ 3.2
K. The experimental and theoretical calculation results suggest that the
emergence of superconductivity in La3Ru8B6 attributes to the rather large
density of states at EF when compared to other two compounds.
