Synthesis, structure and physical characterization of the structural transitions in CePd₃Sn and LaPd₃Sn polymorphs

Ternary stannides CePd₃Sn and LaPd₃Sn were synthesized by arc melting the elements. Their crystal structures determined at room temperature revealed a new structure type: sp. gr. Cmcm, Z = 4, a = 4.5160(18) Å, b = 15.878(8) Å, c = 5.396(3) Å for CePd₃Sn and a = 4.5187(10) Å, b = 15.961(5) Å, c = 5.451(2) Å for LaPd₃Sn. The new type of structure can be presented as built of two types of slabs stacked along the b-axis – CePdSn slab of PbFCl-type and palladium corrugated slab. CePd₃Sn and LaPd₃Sn undergo reversible crystal structure phase transition at 141 K and 260 K, respectively. The temperature hysteretic behavior through the transition is tracked with electrical resistivity and magnetic susceptibility. Single-crystal X-ray diffraction data at 120 K showed that the low-temperature (LT) polymorph of CePd₃Sn crystallizes in the monoclinic structure type, with C2/m space group, Z = 16 and lattice parameters a = 10.8314(7) Å, b = 9.0474(5) Å, c = 15.8725(12) Å, β = 91.325(6)°. LT−CePd₃Sn is found to order at low temperature into a putative antiferromagnetic spin structure below 1 K.