Fermi surface properties of CeRu2(Si1-xGex)2 in magnetic fields above the metamagnetic transitions

We report de Haas-van Alphen effect measurements on CeRu(2)(Si(1-x)Ge(x))(2) to reveal electronic structure change over the broad range of chemical pressure from x = 0.0 to 1.0. It is found that the Fermi surface properties change drastically across the metamagnetic crossover field (B(m)) but vary smoothly with x from those in magnetic fields above B(m) in CeRu(2)Si(2) to those in the ferromagnetic state in CeRu(2)Ge(2). Implications of the present results are discussed in conjunction with the magnetic phase diagram.