A Novel Magnetic Material by Design: Observation of Yb³⁺ with Spin-1/2 in Yb Pt₅P

The localized f-electrons enrich the magnetic properties in rare-earth-based intermetallics. Among those, compounds with heavier 4d and 5d transition metals are even more fascinating because anomalous electronic properties may be induced by the hybridization of 4f and itinerant conduction electrons primarily from the d orbitals. Here, we describe the observation of trivalent Yb³⁺ with S = 1/2 at low temperatures in Yb Pt₅P, the first of a new family of materials. Yb Pt₅P (0.23 ≤ x ≤ 0.96) phases were synthesized and structurally characterized. They exhibit a large homogeneity width with the Yb ratio exclusively occupying the 1a site in the anti-CeCoIn₅ structure. Moreover, a sudden resistivity drop could be found in Yb Pt₅P below ∼0.6 K, which requires further investigation. First-principles electronic structure calculations substantiate the antiferromagnetic ground state and indicate that two-dimensional nesting around the Fermi level may give rise to exotic physical properties, such as superconductivity. Yb Pt₅P appears to be a unique case among materials.