CeAgAs2 -: a new derivative of the HfCuSi2 type of structure:: Synthesis, crystal structure and magnetic properties

Single crystals of CeAgAs2 have been obtained by chemical transport reactions starting from a pre-reacted powder sample. The crystal structure was solved using X-ray diffraction (space group Pmca, No. 57, a = 5.7586(4) Angstrom, b = 5.7852(4) Angstrom, c = 21.066(3) Angstrom, Z = 8) and refined to a residual of R(F) = 0.029 for 46 refined parameters and 1020 reflections. The structure of CeAgAs2 represents a new distorted and ordered variant of the HfCuSi2 type. The characteristic feature of this structure are infinite cis-trans chains of As atoms with As-As distances of 2.563(1) Angstrom and 2.601(1) Angstrom. CeAgAs2 is paramagnetic (mu(eff) = 2.37 mu(B), theta = -10.5(2) K), with antiferromagnetic ordering at 5.5(2) K and exhibits a metamagnetic transition starting at 4.6 kOe and T = 1.8 K.