Field-angle-resolved specific-heat measurements were performed on a clean single crystal of a spin-triplet superconductor UTe_2 with T_ c=2.1 K and a low residual electronic specific heat. At low temperatures, the specific heat exhibits a linear dependence on the magnetic field when the field is applied precisely along the b axis, in stark contrast to its rapid increase at low fields for other orientations. This pronounced anisotropy suggests the presence of nodal quasiparticle excitations with the Fermi velocity predominantly aligned along the b axis. Considering the characteristic field-angle dependences of both the specific heat and the upper critical field, these observations are broadly compatible with theoretical models that assume a superconducting gap structure featuring either point nodes consistent with B_ 2u symmetry, allowed in the infinitely strong spin-orbit coupling scheme, or line nodes confined to flat regions of the quasi-two-dimensional Fermi surface, consistent with ^3B_ 3u symmetry in the finite spin-orbit classification scheme. These results yield crucial hints for resolving the pairing symmetry of UTe_2, paving the way for a deeper understanding of its spin-triplet superconductivity.
To enhance the poor pitting corrosion resistance of sintered CrMnFeCoNi high-entropy alloys (HEAs), methods of increasing the Cr content and applying solution treatment to the alloys were employed, and the material characterization and polarization in NaCl solution were investigated. All as-sintered alloys exhibited Cr-rich zones with elevated oxygen, carbon, and manganese concentrations. While increasing the Cr content to 36
