Magnon Gap Formation of Antiferromagnetic Topological Weyl semimetal in La0.1Eu0.9BiTe3

Correlated magnon excitations in topologically non-trivial systems remain largely unexplored experimentally. Here, we report that 10% La-substituted single crystal La₀.₁Eu₀.₉BiTe₃ simultaneously host antiferromagnetic order (T _N = 7 K) and a topological Weyl-semimetallic state with following a magnon gap formation. Magnetic susceptibility and low-temperature specific-heat measurements reveal a field-dependent minimum at T _M = 5 K and a finite magnon gap that softens with increasing magnetic field-signatures of magnon gap formation. Electrical transport, including planar Hall measurements, follows semiclassical Boltzmann theory yet violates conventional Lorentz-force behavior, reflecting nontrivial Berry curvature effects. Angle-resolved photoemission spectroscopy directly visualizes linearly dispersive bulk bands and isolated two-fold-degenerate Weyl nodes. These results establish La₀.₁Eu₀.₉BiTe₃ as a versatile platform for investigating the interplay between correlated magnetic excitations and topological Weyl phases.