Controlling the Chern Number by Hand (IMAGE) Paul Scherrer Institute Caption Crystals of PdGa can be grown with two distinct structural chiralities (left and right column). The two enantiomers have mirrored crystal structures (second row), as seen in electron-reflection patterns (third row). Schröter et al. now demonstrate that the handedness are reflected as well in the structure of the Fermi surfaces (bottom row), which determine the electronic behaviour of the material. Both compounds display the maximal Chern number, but with opposite sign, +4 and -4, respectively. (Adapted from ref. 1.) Credit Paul Scherrer Institute/Niels Schröter Usage Restrictions All media, such as photos, graphics and videos may only be used in the editorial context of these contents, naming the author. Archiving of this media is not permitted. License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.