The new cubic compound Fe 0.5 Ni 0.5 P 3 (a = 775.29(5) pm) as well as the known compounds CoP 3 and NiP 3 were synthesized from the elemental components using tin as a flux. Their skutterudite (CoAs 3 ) type structures were refined from single-crystal X-ray data. The new compound GdFe 4 P 12 was prepared by reaction of an alloy Gd 1/3 Fe 2/3 with phosphorus in a tin flux. Its cubic ªfilledº skutterudite (LaFe 4 P 12 type) structure was refined from single-crystal X-ray data: a = 779.49(4) pm, R = 0.019 for 304 structure factors and 11 variable parameters. SmFe 4 P 12 shows Van Vleck paramagnetism while GdFe 4 P 12 is a soft ferromagnet with a Curie temperature of T C = 22(5) K. Both are metallic conductors. The new isotypic polyarsenide NdFe 4 As 12 (a = 830.9(1) pm) was obtained by reacting NdAs 2 with iron and arsenic in the presence of a NaCl/KCl flux. The new isotypic polyantimonide Eu 0.54(1) Co 4 Sb 12 (a = 909.41(8) pm) was prepared by reaction of EuSb 2 with cobalt and antimony. Its structure was refined from singlecrystal X-ray data to a residual of 0.024 (137 F values, 12 variables). A comparison of the Fe±P and P±P bond lengths in the compounds AFe 4 P 12 , where the A atoms (A = Ce, Eu, Gd, Th) have differing valencies, suggests that the Fermi level cuts through Fe±P bonding and P±P antibonding bands.