INVAR-LIKE BEHAVIOR OF HEAVY ELECTRONS IN CE(RU0.85RH0.15)(2)SI-2

Lattice thermal expansion was measured for the single crystals of mixe d compound Ce(Ru0.85Rh0.15)(2)Si-2 along the alpha- and c-axes between 4 and 300 K. Below about 50 K, the lattice constant of the unit cell largely contracts due to the Kondo effect. On the other hand, below T- N similar to 5.5 K which is the ordering temperature of a spin density wave, the contraction becomes very small. The temperature dependence of the ordered moment was estimated from the neutron scattering intens ity. The change of the lattice contraction around 5 K associated with the increase of the ordered moment is similar to the one which has bee n observed for 3d-transition metal INVAR alloys.