Superconducting gap structure of the skutteruditeLaPt4Ge12probed by specific heat and thermal transport

We investigated the superconducting order parameter of the filled skutterudite ${\mathrm{LaPt}}₄{\mathrm{Ge}}₁₂$, with a transition temperature of ${T}_c=8.3$ K. To this end, we performed temperature and magnetic-field dependent specific-heat and thermal-conductivity measurements. All data are compatible with a single superconducting $s$-wave gap. However, a multiband scenario cannot be ruled out. The results are discussed in the context of previous studies on the substitution series ${\mathrm{Pr}}_{1\ensuremath{-}x}{\mathrm{La}}_x{\mathrm{Pt}}₄{\mathrm{Ge}}₁₂$. They suggest compatible order parameters for the two end compounds ${\mathrm{LaPt}}₄{\mathrm{Ge}}₁₂$ and ${\mathrm{PrPt}}₄{\mathrm{Ge}}₁₂$. This is not consistent with a single $s$-wave gap in ${\mathrm{LaPt}}₄{\mathrm{Ge}}₁₂$ considering previous reports of unconventional and/or multiband superconductivity in ${\mathrm{PrPt}}₄{\mathrm{Ge}}₁₂$.