Uniaxial Fermi-surface nesting and spin-density-wave transition in the heavy-fermion compound Ce(Ru0.85Rh0.15)2Si2

Abstract

Resistivity parallel and perpendicular to the tetragonal $c$ axis of the antiferromagnetic heavy-fermion compound $\mathrm{Ce}({\mathrm{Ru}}_{1-x}{\mathrm{Rh}}_x{)}_2{\mathrm{Si}}_2$ for $x=0.15\mathrm{}$ has been measured in various fields along the $c$ axis of the single crystal. A sharp upturn is observed just below the Néel temperature $T_N$ only in the parallel direction. This is interpreted in terms of partial gapping of the Fermi surface along the uniaxial $c$ direction. The specific heat and susceptibility below $T_N$ are, respectively, analyzed into two independent contributions in the low-temperature limit: one is 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-fermion contribution due to the remaining ungapped part of about 65%. These facts suggest an itinerant spin-density-wave transition based on Fermi-surface nesting in a heavy-electron band.