Anisotropic superconducting phase diagram of C6Ca

We present a study of the anisotropic superconducting phase diagram of the new carbon intercalation superconductor C6Ca using magnetization and specific heat measurements. We observe an onset of superconductivity at 11.3 K and a transition width of about 1 K from heat capacity and low-field magnetization measurements. A clear step in the heat capacity confirms the bulk nature of the superconducting state. We determined an in-plane coherence length of ξab ≈ 36 nm and an anisotropy parameter of the coherence length of Γ ≈ 3.5–4.