  A structural and thermodynamic study of the newly synthesized single crystal
Sr5Rh4O12 is reported. Sr5Rh4O12 consists of a triangular lattice of spin
chains running along the c-axis. It is antiferromagnetically ordered below 23 K
with the intrachain and interchain coupling being ferromagnetic (FM) and
antiferromagnetic (AFM), respectively. There is strong evidence for an Ising
character in the interaction and geometrical frustration that causes incomplete
long-range AFM order. The isothermal magnetization exhibits two step-like
transitions leading to a ferrimagnetic state at 2.4 T and a FM state at 4.8 T,
respectively. Sr5Rh4O12 is a unique frustrated spin-chain system ever found in
4d and 5d based materials without a presence of an incomplete 3d-electron
shell.
