Low-Temperature Susceptibility of the Noncentrosymmetric Superconductor CePt₃Si

We report ac susceptibility measurements of polycrystalline CePt₃Si down to 60 mK and in applied fields up to 9 T. In a zero applied field, a full Meissner state emerges at temperatures T/T_c<0.3, where T_c=0.65  K is the onset transition temperature. Though transport measurements show a relatively high upper critical field B_c2∼4–5  T, the low-temperature susceptibility χ^′ is quite fragile to the applied field, with χ^′ diminishing rapidly in fields of a few kG. Interestingly, the field dependence of χ^′ is well described by the power law 4πχ^′+1=(B/B_c)^1/2, where B_c is the field at which the onset of resistance is observed in transport measurements.