Anisotropic s-wave superconductivity in single crystals CaAlSi from   penetration depth measurements
  In- and out-of-plane London penetration depths were measured in single crystals CaAlSi (T_{c}=6.2 K and 7.3 K) using a tunnel-diode resonator. A full 3D BCS analysis of the superfluid density is consistent with a prolate spheroidal gap, with a weak-coupling BCS value in the ab-plane and stronger coupling along the c-axis. The gap anisotropy was found to significantly decrease for higher T_{c} samples. 
Ruslan Prozorov, Tyson A. Olheiser, Russell W. Giannetta, Kentaro   Uozato, Tsuyoshi Tamegai