The actinide-platinum binaries Th3Pt4 and U3Pt4: Crystallographic investigation and heavy-fermion behavior of the ferromagnetically ordered U3Pt4

•The novel phases A3Pt4 (A = Th, U) crystallizes with the Pu3Pd4 structure-type.•U3Pt4 orders ferromagnetically below TC = 6.5(10) K.•U3Pt4 exhibits a heavy fermion behavior (γ = 246(2) mJ molU−1 K−2).

The existence of the binary compounds Th3Pt4 and U3Pt4 has been established in the course of the reinvestigation of the U-Pt and Th-Pt systems. Their structural and physical properties have been studied for the first time. Both compounds solidify from the melt of the elemental components with the stoichiometric ratio. Rietveld refinements reveal that they both adopt the trigonal Pu3Pd4 structure type (R3¯ space group) with lattice parameters at room temperature of a = 13.6870(3) Å, c = 5.7991(2) Å for Th3Pt4 and a = 13.2380(2) Å, c = 5.6808(2) Å for U3Pt4. Magnetic and specific heat measurements show that Th3Pt4 behaves as a typical metal; it was further used as phonon analogue of the U-counterpart. U3Pt4 undergoes a ferromagnetic ordering below TC = 6.5(5) K. Its low temperature specific heat is dominated by an enhanced Sommerfeld coefficient (246(2) mJ molU−1 K−2) classifying this phase into the heavy fermion family.

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