The quantum Hall effect (QHE), which was previously known for two-dimensional (2-D) systems, was predicted to be possible for three-dimensional (3-D) systems by Bertrand Halperin in 1987, but the theory was not proven until recently by researchers from the Singapore University of Technology and Design (SUTD) and their research collaborators from around the globe.
Source:
https://phys.org/news/2019-08-three-dimensional-quantum-hall-effect.html