Fermi surfaces of the nodal-line candidates CaCdGe and CaCdSn: Discrepancy between band structure calculations and quantum oscillation measurements

Nodal-line semimetals are characterized by one-dimensional lines or loops of topologically protected band-touching nodes. For two recent nodal-line semimetal candidates, CaCdGe and CaCdSn, band structure calculations show nontopological and topological valence bands with the nodal band crossings above the Fermi level. Here, we present our investigation of the Fermi surfaces of CaCdGe and CaCdSn by use of de Haas–van Alphen measurements and band structure calculations. Our measurements reveal many quantum oscillation frequencies that are not predicted by calculations. This discrepancy casts doubt on the calculated band structures and, thus, on the precise nature of the topology of these systems. Published by the American Physical Society 2025