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 11.3K and a transition width of about 1K 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≈36nm and an anisotropy parameter of the coherence length of Γ≈3.5–4.