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Abstract:
New observations are reported for the heavy-fermion superconductors CeCu
2Si 2, UBe 13 and UPt 3. These results are discussed with respect to the
following issues: (i) the competition between different cooperative
phenomena in CeCu 2Si 2; (ii) the question whether the whole Fermi
surface contributes to the superconducting transition in the three
compounds; (iii) the nature of the superconducting order parameter.
Taking into account more published data for these systems, the author
can delineate the present status of the field: CeCu 2Si 2 behaves as a
singlet superconductor with possibly anisotropic Cooper pairing. UPt 3
appears to possess an anisotropic order parameter, either of the singlet
or triplet type. No definite conclusions can yet be drawn for UBe 13,
mainly because its superconducting properties are severely modified by
field and temperature dependences of the normal-state parameters.
