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Y. Kawamura, S. Deminami, L. Salamakha, A. Sidorenko, P. Heinrich, H. Michor, E. Bauer, C. Sekine:
"Filled skutterudite superconductor CaOs₄P₁₂ prepared by high-pressure synthesis";
Physical Review B, 98 (2018), 024513; 1 - 7.

In this paper,wereport the transport, thermodynamic, and superconducting properties of a newfilled skutterudite CaOs₄P₁₂ synthesized under high pressure and high temperature. The electrical resistivity of 3.4-4.8 mΩcm, carrier concentration of 3.8-6.1 × 1020cm⁻³, and positive Hall coefficient suggest that CaOs₄P₁₂ is a semimetal with hole carriers. An anomaly due to low-energy optical modes corresponding to an Einstein temperature of 150 K was observed in the specific heat. Resistivity, dc magnetic susceptibility, and specific heat measurements indicate bulk superconductivity below 2.5 K. The specific heat anomaly at Tc, ΔC/γTc ≈ 1.4, is in agreement with the Bardeen-Cooper-Schrieffer (BCS) value of 1.43. The electron-phonon coupling constant λ_ep is estimated to be 0.47. CaOs₄P₁₂ is classified as a BCS-type, weakly coupled type-II superconductor with an upper critical field of H_c2 ≈ 22 kOe and Ginzburg-Landau coherence length of ξ ≈ 12 nm.

http://dx.doi.org/10.1103/PhysRevB.98.024513