The Superconducting Gap Behavior in the Antiferromagnetic   Nickel-Borocarbide Compounds RNi2B2C (R=Dy, Ho, Er, Tm) Studied by   Point-Contacts Spectroscopy
  An general survey of the superconducting (SC) gap study in the title compounds by point-contact (PC) spectroscopy is presented. The SC gap was determined from dV/dI of PCs employing the well-known theory of conductivity for normal metal-superconductor PCs accounting Andreev reflection. The theory was modified by including pair-breaking effects considering the presence of magnetic rare-earth ions. A possible multiband structure of these compounds was also taken into account. The PC study of the gap in the Er-compound (TN=6K<Tc=11K) gives =evidence for the presence of two SC gaps. Additionally, a distinct decrease of both gaps is revealed for R = Er in the antiferromagnetic (AF) state. For R = Tm (TN=1.5K<Tc=10.5K) a decrease of the SC gap is observed below 4-5K, while for R = Dy (TN=10.5K>Tc=6.5K) the SC gap has a BCS-like dependence in the AF state. The SC gap for R = Ho (TN=5.2K<Tc=8.5K) exhibits below T*=5.6K a single-band BCS-like dependence vanishing above T*, where a specific magnetic order occurs. The difference in the SC gap behavior in the title compounds is attributed to different AF ordering. 
Yu. G. Naidyuk, G. Behr, N. L. Bobrov, V. N. Chernobay, S.-L.   Drechsler, G. Fuchs, O. E. Kvitnitskaya, D. G. Naugle, K. D....