b'Electronic andFirst-ever synthesis and characterization of neptunium telluride transport propertiessingle crystals advances the fundamental understanding of of single-crystallineelectronic correlations and topology in neptunium telluride.neptunium telluride T he project led to the first-ever synthesis of neptunium telluride (NpTe 2-x ) single crystals using the iodine vapor transport method. Single crystal x-ray diffraction and energy dispersive spectroscopy measurements showed that these crystals form in the layered tetragonal uranium arsenide type structure with vacancies on the tellurium site at x0.25. Magnetic susceptibility measurements uncovered anisotropic Curie paramagnetism, where the application of the Curie-Weiss model to the data yields an effective magnetic momenteff= PROJECT NUMBER:3.6B /Np. Such a finding is consistent with expectations for neptunium (Np) being 22P1068-012FP in a tetravalent state (Np 4+electronic configuration). A gradual deviation from the Curie-Weiss behavior seen at low temperatures may be due to hybridization between TOTAL APPROVED AMOUNT:the f- and conduction electron states or crystal electric field effect. Heat capacity $125,000 over 1 year measurements revealed enhanced mass Fermi liquid behavior at low temperatures, PRINCIPAL INVESTIGATOR:as well as evidence for a possible phase transition at T = 1.5 K. Together with Krzysztof Gofryk, INL electrical resistivity measurements that show semimetallic behavior, these results indicate that hybridization between the f- and conduction electron states CO-INVESTIGATORS: dominates the physics of NpTe 1.75 , leading to a hybridization gap semimetal. The low Daniel Murray, INL temperature electrical resistivity and preliminary electronic structure calculations Narayan Poudel, INL might indicate the presence of a non-trivial electronic structure in this material. COLLABORATORS: These new results are crucial for the fundamental understanding of the effect of Colorado School of Mines electronic correlations and topology in transuranic materials and might represent a Florida State University first example of such behavior in these materials.National High Magnetic Field LaboratoryPRESENTATIONS:Krzysztof Gofryk, Jean-Christoph Griveau, James L Smith, Transport properties of strongly correlated compounds AnPd 3(An = Pu, Np), American Physical Society meeting, March 20-22, 2023.William L Nelson, Ashini S Jayasinghe, Joseph M Sperling, Nicholas Beck, Todd N Poe, Daniel Murray, Narayan Poudel, Rory Kennedy, Susan Latturner, Thomas E Albrecht-Schoenzart, Ryan E Baumbach, and Krzysztof Gofryk, Kondo Lattice Semimetallic Behavior in NpTe 1.75Single Crystals, American Physical Society meeting, March 20-22, 2023.Temperature-dependent electrical resistivity, (T), of a NpTe 1.75single crystal. The dashed line is a fit to the data that considers two conductivity channels (metallic and semiconducting) with an energy gap ~35 meV. The inset shows an image of the NpTe 1.75lamella prepared by the plasma focused ion beam method and used for the resistivity measurements with platinum wires attached to the sample.141'