The quantum mechanical (Berry) phase of the electronic wavefunction plays a critical role in the anomalous 1,2 and spin Hall e ects 3,4 , including their quantized limits 5-7 . While progress has been made in understanding these e ects in ferromagnets 8 , less is known in antiferromagnetic systems. Here we present a study of antiferromagnet GdPtBi, whose electronic structure is similar to that of the topologically non-trivial HgTe (refs 9-11), and where the Gd ions o er the possibility to tune the Berry phase via control of the spin texture. We show that this system supports an anomalous Hall angle Θ AH > 0.1, comparable to the largest observed in bulk ferromagnets 12 and significantly larger than in other antiferromagnets 13 . Neutron scattering measurements and electronic structure calculations suggest that this e ect originates from avoided crossing or Weyl points that develop near the Fermi level due to a breaking of combined timereversal and lattice symmetries. Berry phase e ects associated with such symmetry breaking have recently been explored in kagome networks 14-17 ; our results extend this to half-Heusler systems with non-trivial band topology. The magnetic textures indicated here may also provide pathways towards realizing the topological insulating and semimetallic states 9-11,18,19 predicted in this material class.The ordinary Hall effect is due to the Lorentz force bending of charge carriers perpendicular to a magnetic field. In systems where time-reversal symmetry (TRS) is spontaneously broken, it typically can be overwhelmed by a different class of mechanisms for transverse velocity. In such systems, there are contributions to transverse velocity from both extrinsic effects due to spindependent scattering 13 and intrinsic effects related to real space 20,21 and momentum space 2 Berry phase mechanisms. The former is relevant in systems with non-coplanar spin textures with finite scalar spin chirality χ ijk = S i · (S j × S k ), where S n are spins, while the latter generically occurs in TRS-broken systems originating from the spin-orbit-interaction-induced Berry curvature of the filled bands. The anomalous Hall effect (AHE) due to magnetic texture is most often associated with finite χ ijk and tends to exhibit relatively small anomalous Hall angles Θ AH 0.01 (such as SrFeO 3 (ref. 22) or Pr 2 Ir 2 O 7 (ref. 23)), while intrinsic band-structure-based effects are common in ferromagnetic systems and can be significantly larger 13 . Recent theoretical work has suggested that effects that rely on both magnetic texture and strong spin-orbit coupling may exist in noncollinear antiferromagnets that lead to significant Hall responses 14 . Single-crystal studies of Mn 3 Sn and Mn 3 Ge have been shown to support Θ AH 0.02 and 0.05, respectively, originating from its inverse triangular spin structure and electronic structure 16,17 .Here we study single crystals of GdPtBi, a member of the family RPtBi (R is a rare earth element) known to exhibit antiferromagnetic ordering 24 . As shown in Fig. 1a, this syste...

Advances in low-dimensional superconductivity are often realized through improvements in material quality. Apart from a small group of organic materials, there is a near absence of clean-limit two-dimensional (2D) superconductors, which presents an impediment to the pursuit of numerous long-standing predictions for exotic superconductivity with fragile pairing symmetries. We developed a bulk superlattice consisting of the transition metal dichalcogenide (TMD) superconductor 2H-niobium disulfide (2H-NbS2) and a commensurate block layer that yields enhanced two-dimensionality, high electronic quality, and clean-limit inorganic 2D superconductivity. The structure of this material may naturally be extended to generate a distinct family of 2D superconductors, topological insulators, and excitonic systems based on TMDs with improved material properties.

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