Andreev Reflection to Probe Momentum-Dependent Spin Polarization in Altermagnet CrSb

Altermagnetic materials have recently emerged as promising candidates for next-generation spintronic applications, characterized by the k-dependent spin-splitted band structure and a simultaneous zero-net-magnetization. Among them, altermagnetic candidate CrSb has attracted considerable attention, owing to its g-wave spin splitting and high Néel temperature. In this Letter, we employed mechanical point-contact spectroscopy with superconducting Nb tips to probe the Andreev reflection on CrSb single crystals along three principal crystallographic orientations. The extracted momentum-dependent spin polarizations are approximately 73.4% for the (0001) plane, 67.9% for the (1[over ¯]1[over ¯]20) plane, and 61.9% for the (101[over ¯]0) plane, respectively, distinct from conventional antiferromagnets. Furthermore, conductance spectra from spatial linescans on the sample surface support the existence of altermagnetic domains with a characteristic size of 250-500 nm separated by domain walls with width about 250 nm. These results strongly support the momentum-dependent spin polarization in altermagnetic CrSb and establish Andreev reflection as a new paradigm to probe k-dependent spin textures.