Intermediate valence behavior in CeCo9Si4

The novel ternary compound CeCo9Si4 has been studied by means of specific heat, magnetization and transport measurements. Single-crystal X-ray refinements reveal a fully ordered distribution of Ce, Co and Si atoms with the tetragonal space group I4/mcm isostructural with other RCo9Si4. The smaller lattice constants of CeCo9Si4 in comparison with the trend established by other RCo9Si4 is indicative for intermediate valence of cerium. While RCo9Si4 with R = Pr,... Tb, and Y show ferromagnetism and LaCo9Si4 is nearly ferromagnetic, CeCo9Si4 remains paramagnetic even in external fields as large as 40T, though its electronic specific heat coefficient (gamma similar or equal to 190 mJ/mol K-2) is of similar magnitude as that of metamagnetic LaCo9Si4 and weakly ferromagnetic YCo9Si4. (c) 2005 Elsevier B.V. All rights reserved.