UNIAXIAL FERMI-SURFACE NESTING AND SPIN-DENSITY-WAVE TRANSITION IN THE HEAVY-FERMION COMPOUND CE(RU0.85RH0.15)(2)SI-2

Resistivity parallel and perpendicular to the tetragonal c axis of the antiferromagnetic heavy-fermion compound Ce(Ru1-xRhx)(2)Si-2 for x=0. 15 has been measured in various fields along the c axis of the single crystal. A sharp upturn is observed just below the Neel temperature T- N only in the parallel direction. This is interpreted in terms of part ial gapping of the Fermi surface along the uniaxial c direction. The s pecific heat and susceptibility below T-N are, respectively, analyzed into two independent contributions in the low-temperature limit: one i s an exponential contribution of the gapped part of the Fermi surface with the energy gap about 10 K, and the other is a residual heavy-ferm ion contribution due to the remaining ungapped part of about 65%. Thes e facts suggest an itinerant spin-density-wave transition based on Fer mi-surface nesting in a heavy-electron band. [S0163-1829(97)00241-5].