Tunnel and point contact experiments have been made in a URu2Si2 single crystal along the c-axis. The experiments were performed changing temperature and contact size in a low temperature scanning tunneling microscope. A resonance develops at the Fermi level at T∼60 K. This resonance splits and becomes asymmetric when the 17.5 K phase transition is crossed. These results are consistent with the existence of Kondo like bound states of the U4+ ionic configurations and the conduction electrons. Below the transition, these configurations are split by the development of quadrupolar ordering. The peak separation can be interpreted as a direct measurement of the order parameter. Measurements on a policrystalline UAu_2Si_2$ sample are also reported, with a comparative study of the behavior of both materials.
@article{arxiv.cond-mat/9609205,
title = {Point-contact spectroscopy on URu$_2$Si$_2$},
author = {J. G. Rodrigo and F. Guinea and S. Vieira and F. G. Aliev},
journal= {arXiv preprint arXiv:cond-mat/9609205},
year = {2016}
}