Abstract

The discovery and characterization of four novel compounds, Ce3ScBi5, Ce2Mn3Bi6, Ce3MnBi9, and Ce1.8Mn3.2Bi5, are reported. Single crystals of these new phases were
synthesized using a bismuth self-flux method. Their crystal structures and chemical compositions were determined using single-crystal and powder X-ray diffraction, complemented by energy-dispersive X-ray spectroscopy.

Ce3ScBi5 crystallizes in the hexagonal Hf5Sn3Cu-type structure with roomtemperature lattice parameters a = 9.6623(2) Å and c = 6.5162(2) Å. It exhibits Kondo lattice behaviour with a coherence temperature T* » 10 K and undergoes two successive antiferromagnetic phase transitions at TN1 = 6.0(1) K and TN2 = 4.1(1) K. Magnetization data reveal strong anisotropy, identifying the c-axis as the hard magnetization direction. The rich magnetic phase diagrams constructed for fields along the [001], [100], and [210] directions highlight the interplay between crystal electric field effect, Kondo coupling, and competing RKKY interactions that give rise to magnetic frustration.

Ce2Mn3Bi6 adopts the monoclinic Sm2Mn3Bi6-type structure (a = 10.4989(3) Å, b = 4.4648(2) Å, c = 13.4649(4) Å, b = 108.694(4)°) and shows metallic conductivity with Fermi liquid behavior below TFL » 10 K, indicating a moderate quasiparticle mass enhancement. Ce3MnBi9 crystallizes in a previously unreported hexagonal structure (space group P63/m, a = 11.908(1) Å, c = 6.424(1) Å) and exhibits metallic resistivity with a distinct kink at ~118(2) K, suggesting a second-order phase transition. Ce1.8Mn3.2Bi5 was identified as an incommensurately modulated phase with an average tetragonal structure (space group P4/nmm, a = 4.5458(2) Å, c = 13.572(1) Å) and modulation vectors sensitive to mechanical treatment.

This work expands the ternary Ce-Mn-Bi phase diagram and provides a foundational study of the structural and electronic properties of the new compounds, paving the way for future investigations.