The compounds of rare-earth metals with rhodium and boron RERhB 4 (RE=Y, Dy–Lu) crystallize with the orthorhombic structure type YCrB 4 (space group Pbam, Pearson symbol oP24). The crystal structures of the compounds with RE=Y, Er, Tm and Yb were refined by using single-crystal diffraction data. Analysis of chemical bonding for YRhB 4 and YbRhB 4 was performed by electron localizability indicator and by calculation of quantum chemical charges (quantum theory of atoms in molecules). Boron and rhodium form the 3-D polyanion containing planar nets of three-bonded boron atoms interconnected by rhodium along [001]. The interaction of the RE species with the rhodium–boron polyanion is predominantly ionic. Magnetic susceptibility data of TmRhB 4 and YbRhB 4 showed that the RE species are in 4f 12 (Tm) and 4f 13 (Yb) electronic states, respectively. In the low-temperature region, the specific heat revealed a Schottky anomaly for TmRhB 4 while an antiferromagnetic transition is observed at 3.5K for YbRhB 4 . X-ray absorption measurement at the Yb L III edge for YbRhB 4 reveals the 4f 13 state of ytterbium.