Revisiting Ce3Pt4Ge6 – crystal structure and physical properties

Abstract

Structural reinvestigations of Ce₃Pt₄Ge₆ on high quality single crystals revealed additional reflections contradicting the previously reported structure featuring half occupied crystallographic sites for this compound. The structure could be solved and refined in the orthorhombic (3 + 1)D superspace group Cmcm(α,0,0)0s0 with α = 0.5a* and lattice parameters of a = 441.17(2), b = 2618.26(14) and c = 441.33(2) pm using the super space approach. The description of the modulated structure as commensurate case allows for an ordering of the Ce2/Ge3 atoms and the respective voids caused by the 50% occupation. The corresponding approximant can be described in the orthorhombic crystal system with space group Pnma and lattice parameters of a = 2618.26(14), b = 441.33(2) and c = 882.34(2) pm. Investigations of the magnetic properties revealed a magnetic moment of μ_eff = 2.48(1)μ_B/Ce atom and a Weiss constant of θ_p = −39(5) K, indicating stable trivalent cerium. No clear magnetic ordering was evident from the susceptibility measurements. Heat capacity investigations showed a λ-shaped anomaly at T = 2.1(1) K. Resistivity measurements show values corresponding to Ce₃Pt₄Ge₆ being a metal, however nearly temperature independent behavior is observed down to low temperatures. A shallow minimum and an abrupt drop suggest the title compound to be a Kondo material.