Anisotropic s-wave superconductivity and peak effect in single crystals CaAlSi

In- and out- of plane London penetration depths were measured in single crystals of CaAlSi by using radio-frequency resonant technique. The obtained temperature variation of the anisotropic superfluid density can be explained by an ellipsoidal s-wave gap with a weak-coupling BCS value in the ab-plane and larger gap amplitude in the c-direction. In a mixed state, similar measurements yield Campbell length, which was used to study the peak effect (PE) in the critical current. The position of the PE line on an H-T phase diagram, the influence of anisotropy and sample parameters are discussed.