  The properties of Pt-based materials can be intriguing due to the importance
of spin-orbit coupling for Pt. Herein, we report four new phases with formulas
M3Pt23Ge11 (M = Ca, Sr, Ba and Eu), which adopt the same structure type as
Ce3Pt23Si11. Magnetic susceptibility measurements indicate that none of the
phases is superconducting above 1.8 K, while for Eu3Pt23Ge11 ferromagnetic
ordering is observed at ~ 3 K. The low Curie temperature for that material
compared to that of Eu3Pt23Si11 may be due to its larger Eu-Eu distance. One
potential factor that destabilizes the structure of other rare-earth based
M3Pt23Ge11 is demonstrated through COHP calculations.
