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CePd3 is Uranium Silicide structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Ce is bonded to twelve equivalent Pd atoms to form a mixture of corner and face-sharing CePd12 cuboctahedra. All Ce–Pd bond lengths are 2.95 Å. Pd is bonded in a distorted square co-planar geometry to four equivalent Ce atoms.
(CePd3)8Ge crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Ce is bonded to twelve Pd atoms to form CePd12 cuboctahedra that share corners with twelve equivalent CePd12 cuboctahedra, faces with six equivalent CePd12 cuboctahedra, and a faceface with one GePd6 octahedra. There are nine shorter (2.99 Å) and three longer (3.01 Å) Ce–Pd bond lengths. There are three inequivalent Pd sites. In the first Pd site, Pd is bonded in a 4-coordinate geometry to four equivalent Ce atoms. In the second Pd site, Pd is bonded in a distorted rectangular see-saw-like geometry to four equivalent Ce atoms. In the third Pd site, Pd is bonded in a 5-coordinate geometry to four equivalent Ce and one Ge atom. The Pd–Ge bond length is 2.52 Å. Ge is bonded to six equivalent Pd atoms to form GePd6 octahedra that share faces with eight equivalent CePd12 cuboctahedra.
We present, for the first time, the thermoelectric properties of NpPd3 and PuPd3 compounds. We show that the Seebeck coefficient of these materials is enhanced and its magnitude and temperature dependence are characteristic of dense Kondo systems in which 5f -states are present in the vicinity of the Fermi level. The electrical resistivity also shows characteristic behavior of Kondo lattices in these materials. For cubic NpPd3 a sharp transition in electrical resistivity and thermopower together with a change of sign of S (T) at the Néel temperature, indicate a first order nature of the magnetic transition. This transition is probably accompanied by a large Fermi-surface reconstruction. Further studies, however, are required to better understand the electronic structure of cubic NpPd3 and other AnPd3 phases. We have also estimated power factor (S^2/rho) of the samples studied. We find out that it is relatively high although much smaller than observed in rare-earth-based REPd3 phases, especially CePd3.