We report the effects of La substitution on the superconducting state of the heavy-fermion superconductor as seen in transport and magnetization measurements. As opposed to the case of conventional superconductors, pair breaking by nonmagnetic La results in the depression of and indicates a strong gap anisotropy. The upper critical field values decrease with increased La concentration, but the critical field anisotropy, does not change in The electronic system is in the clean limit for all values of x.
- Received 1 April 2002
- Published 29 August 2002
© 2002 The American Physical Society