Publication Type
Journal
Journal Name
Physical Review Letters
Publication Date
Page Number
207001
Volume
106
Issue
20
Abstract
The tetragonal heavy-fermion compound \ccs\ exhibits a superconducting ground state (S type, $T_c=0.67$ K) close to a magnetic instability. Here, we present angle-resolved resistivity measurements of the upper critical field \hc. In-plane rotation of S-type \ccs\ single crystals reveals a four-fold oscillation of $H_{c2}$. An extended weak-coupling BCS model for a d-wave symmetry including strong Pauli-limiting effects confirms the aforementioned angular dependence and points towards d$_{xy}$ symmetry of the order parameter.
