Heavy quasiparticles in the ferromagnetic superconductor ZrZn2
  We report a study of the de Haas-van Alphen effect in the normal state of the ferromagnetic superconductor ZrZn2. Our results are generally consistent with an LMTO band structure calculation which predicts four exchange-split Fermi surface sheets. Quasiparticle effective masses are enhanced by a factor of about 4.9 implying a strong coupling to magnetic excitations or phonons. Our measurements provide insight in to the mechanism for superconductivity and unusual thermodynamic properties of ZrZn2. 
S.J.C. Yates, G. Santi, S.M. Hayden, P.J. Meeson, and S.B. Dugdale