Two-dimensional Sb net generated nontrivial topological states in SmAgSb₂ probed by quantum oscillations

The REAgSb₂ (RE = rare earth and Y) family has drawn considerable research interest because the two-dimensional Sb net in their crystal structures hosts topological fermions and hence rich topological properties. We report herein the magnetization and magnetotransport measurements of SmAgSb₂ single crystal, which unveil very large magnetoresistance and high carrier mobility up to 6.2 × 10³% and 5.58 × 10³ cm²⋅V⁻¹⋅s⁻¹, respectively. The analysis of both Shubnikov–de Haas and de Haas–van Alphen quantum oscillations indicates nontrivial Berry phases in the paramagnetic state while trivial Berry curvature in the antiferromagnetic state, indicating a topological phase transition induced by the antiferromagnetic order. It is also supported by the first-principles calculations. The results not only provide a new interesting topological material but also offer valuable insights into the correlation between magnetism and nontrivial topological states.