Chiral anomaly and weak antilocalization effects in the Weyl semimetal EuAuSb

Topological materials with nontrivial spin structure have received considerable attention because they exhibit varieties of novel quantum phenomena. Here, we report a combined experimental and theoretical study of magnetic and magnetotransport properties of EuAuSb, an itinerant antiferromagnet with low N\'eel temperature, TN~ 3.5 K. The concomitant change in the field and temperature dependence of the electrical resistivity and that of the magnetization suggest that the charge conduction mechanism in EuAuSb is strongly influenced by the spin configuration of the Eu. Below TN, both longitudinal magnetoresistance (LMR) and transverse magnetoresistance (TMR) are large and positive at low fields, but negative at high fields. TMR becomes positive above 20 K, while LMR remains negative up to the highest measured temperature of 100 K. The negative LMR well above the TN is attributed to the chiral anomaly associated with the Weyl fermion state, while the low-field positive LMR and TMR are due to the weak antilocalization (WAL) effect. The WAL effect in TMR can be described well by the Hikami-Larkin-Nagaoka model, while the WAL effect in LMR is explained using the generalized Altshuler-Aronov model. The Hall resistivity indicates that holes are the majority charge carriers in EuAuSb with concentration ~10²⁰4pt0excm^-3 and mobility ~10³4pt0excm²0.16em0exV^-10.16em0exs^-1 (at 2 K). The Shubnikov--de Haas oscillation in TMR has been analyzed to determine several important physical parameters related to the Fermi surface of EuAuSb. The detailed analysis unveils the large topological Hall effect, which is attributed to the presence of Weyl fermions and complex magnetic ordering, as confirmed by the $ab$ initio simulation. Our theoretical calculations reveal topologically nontrivial surface Fermi arcs and suggest competition among various low-energy magnetic phases, including an altermagnetic phase, mediated by specific crystalline symmetry present in EuAuSb.