Andreev reflection spectroscopy on the heavy-fermion superconductor   PrOs$_{4}$Sb$_{12}$: Microscopic evidence for multiple superconducting order   parameters
  Point-contact Andreev reflection spectroscopy was performed on single crystals of the heavy-fermion superconductor PrOs$_{4}$Sb$_{12}$, down to 90mK and up to 3Tesla. The conductance spectra showed multiple structures, including zero-bias peaks and spectral dips, which are interpreted as signatures of multiple pairing gaps, one clearly having nodes. Samples with 2% Ru replacing Os were also measured, showing pronounced spectral humps consistent with the emergence of a non-nodal gap. Detailed analysis of the spectral evolution revealed a magnetic field-\emph{vs.}-temperature phase diagram for PrOs$_{4}$Sb$_{12}$ characterized by two distinct superconducting order parameters. 
C. S. Turel, W. M. Yuhasz, R. Baumbach, M. B. Maple and J. Y.T. Wei
cond-mat.supr-con