Anisotropy of penetration depth in superconducting tin

Microwave resonance technique at 3000 MHz has been used to carry out measurements of the temperature variation of penetration depth in single crystals of pure tin. Several samples of known crystallographic orientations have been studied, and the anisotropy of penetration depth obtained. The results clearly show non-tensorial anisotropy of penetration depth, and hence provide a direct experimental evidence for non-local relation between the current density and associated magnetic field in a type I superconductor.