Real-space imaging of surface-magnetism in magnetic Weyl semimetal candidate CeBi*

Magnetic Weyl semimetals host chiral Weyl nodes in their bulk which are formed by broken time-reversal symmetry, caused, for example, by intrinsic ferromagnetic order. While the bulk-surface correspondence dictates the formation of Fermi arcs connecting Weyl nodes with opposite chirality, their momentum-space contour and their connectivity (i.e. which Weyl points they are connecting to), depends on surface properties. Here we use spin-polarized scanning tunneling microscopy to map the magnetic structure on the surface of CeBi at various bulk-magnetic phases. We find unexpected surface-magnetic order with strongly bias-dependent magnetic contrast and phase. We discuss our observation in terms of Fermi arc connectivity and magnetic interactions in CeBi.