Multiband superconductivity in PrPt4Ge12 single crystals

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We report measurements of the London penetration depth Δλ(T) and the electronic specific heat Cₑ(T) on high-quality single crystals of the filled-skutterudite superconductor PrPt₄Ge₁₂ (Tc≃8K). Both quantities show a weak temperature dependence at T≪ Tc, following Δλ Tⁿ (n≃ 3.2) and Cₑ/T T².⁸. Such temperature dependences deviate from both conventional s-wave type and nodal superconductivity. A detailed analysis indicates that the superfluid density ρₛ(T), derived from the penetration depth, as well as the electronic specific heat can be consistently described in terms of a two-gap model, providing strong evidence of multiband superconductivity for PrPt₄Ge₁₂.