Evidence for gap anisotropy in

Resistivity measurements under uniaxial stress have been performed on the intermediate valence compound SmB6 for various directions of the crystal. The experimental technique allows us to explore a limited pressure area (basically 0-3 kbar). Nevertheless, the results clearly show an anisotropy; indeed, the effect of the stress in the decrease of the residual resistivity is much higher in the < 111 > direction than in the < 100 > and the < 110 > orientations. This change is witness to the gap anisotropy which must be linked to the theory of excitonic semiconductors.