High-pressure synthesis and exotic heavy-fermion behaviour of the filled skutterudite SmPt4Ge12

Ternary samarium-filled platinum–germanium skutterudite SmPt4Ge12 was prepared at a pressure of 5.0(0.5) GPa and a temperature of 1070(70) K. The compound crystallizes in the cubic space group (a=8.6069(4) Å) and is isotypic with LaFe4P12. X-ray absorption spectroscopy measurements show that samarium in SmPt4Ge12 has a temperature-independent intermediate valence (ν=2.90±0.03). Magnetization data reveal Van Vleck paramagnetism above ∼50 K. The low-temperature specific heat displays a broad anomaly centred at 2.9 K and a large linear coefficient γ ′ =450 mJ mol− 1 K−2 suggesting heavy-fermion behaviour. Low-temperature electrical resistivity shows a temperature dependence reminiscent of the Kondo effect. Density functional calculations result in an electronic structure that is, apart from the Sm 4f contributions, very similar to LaPt4Ge12.