Realization of practical eightfold fermions and fourfold van Hove singularity in TaCo2Te2

Abstract Space groups describing the symmetry of lattice structure allow emergence fermionic quasiparticles with various degeneracy in band structure. Theoretical efforts have predicted many materials hosting fermions highest degeneracy, i.e., eightfold fermions, yet lacking experimental realization. Here, we explore degeneracies TaCo 2 Te crystals. Through systematic and theoretical analyses, establish as a nonsymmorphic crystal negligible spin–orbit coupling (SOC) long-range magnetic order. These critical properties guarantee realization practical fourfold van Hove singularity, directly observed by photoemission spectroscopy. serves topological quantum platform, which can be tuned into magnetic, topologically trivial, nontrivial phases adding strain, field, or SOC. The latter is demonstrated our first-principles calculations, show that enhancing SOC will promote observation bulk hourglass fermions. Our results platform to interplay between topology.