Anomalous transport properties of Weyl semimetal CeAlSi

Magnetic Weyl semimetals attract significant attention due to their nontrivial band structure and resulting unusual transport properties. Among them are the anomalous Hall and anomalous Nernst effects, which studies offer a look into details of the electronic structure. CeAlSi crystallizes in a non-centrosymmetric space group and exhibits ferromagnetic ordering below the Curie temperature (T_C = 8.5 K). The Weyl points appear in its electronic structure due to broken both inversion and time reversal symmetry. We measured the anomalous Hall conductivity for two different orientations of the magnetic field (B), namely σ_xy for B || a and σ_yz for B || c, where a and c are the magnetically easy and hard axis. In the magnetic phase, σ_xy and σ_yz turn out to be of opposite sign. The sign change of the anomalous Hall effect is attributed to shifting of the Weyl point due to reconstruction of the band structure driven by spin reorientation. We also observed the anomalous contribution in the Nernst conductivity (α_xy) measured for B || c. We were able to recreate the temperature dependences of σ_xy and α_xy in the paramagnetic phase using a single band toy model assuming a non-zero Berry curvature in the vicinity of the Weyl node.Large σ_xy and non-vanishing α_xy in the paramagnetic phase of CeAlSi appear to be consequences of the fact that the Fermi level lies close to the band crossing point.