We present data on the modulation of the critical current with applied magnetic field in UPt_3-Cu-Pb Josephson junctions and SQUIDs. The junctions were fabricated on polished surfaces of UPt_3 single crystals. The shape of the resulting diffraction patterns provides phase sensitive information on the superconducting order parameter. Our corner junction data show asymmetric patterns with respect to magnetic field, indicating a complex order parameter, and both our junction and SQUID measurements point to a phase shift of Pi, supporting the E_2u representation of the order parameter.
@article{arxiv.0907.0225,
title = {Evidence for the E_2u model of the superconducting order parameter in UPt_3 from Josephson interferometry},
author = {J. D. Strand and D. J. Van Harlingen and J. B. Kycia and W. P. Halperin},
journal= {arXiv preprint arXiv:0907.0225},
year = {2009}
}