EuAuSb is a magnetic Weyl semimetal candidate that exhibits in-plane ferromagnetic ordering and a helical magnetic order across the plane at temperatures below 3.9 K. These magnetic characteristics can drive an interaction-induced reconstruction of the Fermi surface. Here, we report a rare instance of Fermi surface splitting and collapsing driven by exchange coupling, as revealed by strongly temperature-dependent quantum oscillation frequencies in EuAuSb. Shubnikov–de Haas measurements reveal two distinct quantum oscillation frequencies ($F_{\alpha }=80\mathrm{T}$ and $F_{\beta }=165\mathrm{T}$) at 2 K. As the temperature increases toward 40 K, the oscillation peaks at these two frequencies gradually merge into a single peak centered around 128 T. This behavior signifies the collapse of the spin-split Fermi surfaces, driven by the weakening of short-range magnetic correlations and the exchange coupling between conduction electrons and local magnetic moments as temperature increases. Our results are further supported by density functional theory calculations, angle-resolved photoemission spectroscopy, and magnetization measurements.

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• Fermi surface
• Magnetic order
• Quantum transport
• Shubnikov-de Haas effect
• Topological phases of matter