ANISOTROPY OF THE GAPPED FERMI-SURFACE OF URU2SI2 IN THE ANTIFERROMAGNETIC STATE STUDIED BY POINT-CONTACT SPECTROSCOPY

The differential resistance dV/dI versus applied voltage for URu2Si2 h omocontacts at helium temperatures shows a distinct maximum at zero bi as for current flow in the ab plane which vanishes as the temperature reaches the Neel temperature T-N similar or equal to 17.5 K. For curre nt flow parallel to the c direction this structure was not so pronounc ed. We connect the observed maximum with the spin-density wave gap ope ning below T-N on part of the Fermi surface in the ab plane. The value of the gap estimated from the width of the zero-bias maxima in the sy mmetric part of the dV/dI is of order 10 meV. The measured temperature dependence shows a rapidly decreasing intensity of this maximum, whil e its width is practically constant up to temperatures close to T-N.