CeCoIn5 is an unconventional heavy fermion superconductor with a relatively large transition temperature Tc = 2.3 K. NMR measurements of the spin lattice relaxation rate at the In(1) site reveal a significant anisotropy of the fluctuating hyperfine fields, which reverses below 30 K. These results suggest that two-dimensional fluctuations of the Ce 4f moments are relevant for the superconducting pairing.
Curro, N. J., & Pines, D. (2007). Anisotropic spin fluctuations in CeCoIn5. Journal of Physics and Chemistry of Solids, 68(11), 2028–2030. https://doi.org/10.1016/j.jpcs.2007.08.020