The systematic presence of the ternary phases U6Mo4Al43 and UMo2Al20 is reported in a U–Mo/Al interaction layer grown by thermal annealing. This work shows, therefore, the low Mo solubility in UAl3 and UAl4 binary phases; it contradicts the hypothesis of the formation of (U,Mo)Al3 and (U,Mo)Al4 solid solutions often admitted in the literature. Using µ‐XAS (micro X‐ray absorption spectroscopy) at the Mo K edge and µ‐XRD (micro X‐ray diffraction), the heterogeneity of the interaction layer obtained on a γ‐U0.85Mo0.15/Al diffusion couple has been precisely investigated. The UMo2Al20 phase has been identified at the closest location from the Al side. Moreover, µ‐XRD mapping performed on an annealed fuel plate enabled the characterization of the four phases resulting from the γ‐U0.85Mo0.15/Al and (U2Mo + α‐U)/Al interactions. A strong correlation between the concentrations of UAl4 and UMo2Al20 and those of UAl3 and U6Mo4Al43 has been shown.

Single crystals of U7Te12 and Th7Te12 were obtained by chemical vapor transport reactions in evacuated and sealed quartz tubes, starting from a slightly deficient tellurium stoichiometry and using iodine as the transporting agent in a temperature gradient of 1030−1000 °C. Their crystal structures were solved in the noncentrosymmetric hexagonal space group P6̄ (No. 174), Z = 1. The cell constants are a = 12.312(1) Å and c = 4.260(1) Å for U7Te12 and a = 12.300(2) Å and c = 4.566(1) Å for Th7Te12. The three nonequivalent actinoid (A = U, Th) atoms per unit cell, A(1), A(2), and A(3), occupy 1a, 3k, and 3j Wyckoff positions and the four nonequivalent tellurium atoms occupy two 3k and two 3j positions. All the actinoid atoms are centered in tricapped (A(1)) or bicapped (A(2), A(3)) tellurium trigonal prisms, which form infinite columns running along the [001] direction. The bicapped trigonal prisms around A(2) and around A(3) are linked also in both cases by edge-sharing, to form large distorted hexacapped trigonal prisms. U7Te12 exhibits ferromagnetic ordering below 54 K and a semimetallic type conductivity.

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