We report on magnetic, transport, and cohesive properties of Er(Co1-xSix)2 compounds in varying
external conditions (T,H,p). The localized Er 4f magnetice moments in ErCo2 order ferromagnetically
below Tc=33 K. The Co 3d band states form no moment above Tc, but below Tc the majority and minority
3d sub-bands split due to strong 4f - 3d exchange interaction Consequently, Co moments of ?1 ?B appear
coupled antiparallel to the Er moments. This is accompanied by a ?50% resistivity drop and an abrupt lattice
expansion. The sharp magnetization, resistivity, and volume anomalies in the critical temperature region
indicate a first order magnetic phase transition.
