CRYSTALLOGRAPHIC AND MAGNETIC-STRUCTURE OF THE NOVEL COMPOUND ERGE1.83

The crystal structure and the magnetic ordering of the novel orthorhom bic compound ErGe2-x has been studied by neutron powder diffraction an d magnetic measurements. The crystal structure belongs to the DyGe1.85 -type (space group Cmc2(1)). ErGe2-x (x = 0.17 (2)) orders antiferroma gnetically below T-N = 6 K and displays a metamagnetic behaviour. The magnetic cell has the same size as the chemical unit cell (q = 0). The magnetic space group is Cmc2(1) (Sh(36)(173)). At T = 1.5 K the magne tic moments of the two erbium sites have the same ordered magnetic mom ent value of 7.63(6)mu(B)/Er and are antiferromagnetically coupled lea ding to an uniaxial structure along the a direction.