We thank B. Bradlyn, J. Cano and M. Aroyo for countless discussions and collaborations, and for their help with the development of the BANDREP section of the BCS, without which none of the present work would have been possible. We thank H. Gross, S. Parkin, U. Schmidt, M. Rampp and the computational resources of the Max Planck Institute at Halle and Garching, as well as the staff at the Atlas supercomputer of the Donostia International Physics Center. We are grateful to H. Lederer and I. Weidl for allowing us access to the Cobra Supercomputer at the Max Planck Gesellschaft (MPG) computing centre. We also thank H. Borrmann of the Max Planck Institute in Dresden for help with the ICSD database. L.E. was supported by the Government of the Basque Country (project IT779-13), the Spanish Ministry of Economy and Competitiveness (MINECO), and the European Fund for Economic and Regional Development (FEDER; project MAT2015-66441-P). M.G.V. was supported by national project IS2016-75862-P of the Spanish MINECO. B.A.B. and Z.W. acknowledge support for the analytical work and ab initio calculations from the Department of Energy (de-sc0016239). B.A.B. and Z.W. acknowledge additional support from a Simons Investigator Award, the Packard Foundation, and the Schmidt Fund for Innovative Research. Z.W. was also supported by the CAS Pioneer Hundred Talents Program. The computational part of the Princeton work was performed under National Science Foundation (NSF) Early-concept Grants for Exploratory Research (EAGER): DMR 1643312 NOA-AWD1004957, ONR-N00014-14-1-0330, ARO MURI W911NF-12-1-0461, NSF-MRSECDMR-1420541.

Reviewer information

Nature thanks Joseph Checkelsky, Marcel Franz and the other anonymous reviewer(s) for their contribution to the peer review of this work.