Dataset - Drastic field-induced resistivity upturns as signatures of unconventional magnetism in superconducting iron chalcogenides

These open access data reflect the data collected as part of the manuscript ”Drastic field-induced resistivity upturns as signatures of unconventional magnetism in superconducting iron chalcogenides”, by Z. Zajicek, I. Paulescu, et al, available on the pre-print server at https://arxiv.org/abs/2512.20862, and to appear in Physical Review B (2026). These ASCII data are associated with a detailed transport study as a function of temperature (2 to 300K) under applied pressure both in zero magnetic field and under applied fixed magnetic fields using a 16T Quantum Design PPMS. Electrical transport measurements were performed on two different high-quality FeSe0.96S0.04 single crystals (S1 and S2) using a standard four-probe configuration to determine the longitudinal resistivity, rho_xx, in the conducting (ab) plane. A maximum a.c. current of 1 mA was applied to the sample, and the magnetic field of up to 16T for sample S1 and 15 T for sample S2 is aligned along the c direction and perpendicular to the applied current, thus probing the transverse magnetoresistance. Transport measurements in constant magnetic fields for sample S2 were performed using different field polarities, and the data were symmetrized afterwards to eliminate any effect of mixing resistivity components. Experiments were carried out under applied pressure using a commercially available BeCu pressure cell from Quantum Design up to 20 kbar while slowly cooling and warming to 2 K at a rate of 0.5 K/min. Hysteresis studies were also performed using 0.25 K/min. Daphne 7373 was used as the pressurizing medium, which is hydrostatic up to 22 kbar. The pressure was determined in situ using the superconducting transition temperature of tin at a slow cooling rate of 0.02 K/min. Resistivity was measured as a function of temperature from a fixed pressure and magnetic field, and each raw data name contains information about the estimated pressure value. Temperature dependence transport studies for sample S2 were performed using different magnetic field polarities and the data were symmetrized afterwards to eliminate any effect of mixing resistivity components.