Abstract
Hg2Os2O7 has been synthesised by direct reaction of HgO, OsO4 and Os metal at 500 °C. The product adopts the pyrochlore structure, in common with Cd2Os2O7, but exhibits a slightly larger lattice parameter at 10.245 Å. The material shows a weak transition to antiferromagnetic behaviour below 88 K; the compound remains semi-metallic through this transition but with a distinct drop in resistivity again centred on 88 K.