Kramers Nodal Lines, Weyl Fermions and Large AHE in SmAlSi

Kramers nodal lines (KNLs) are special type of Weyl line degeneracy that connects time reversal invariant momenta. KNLs are robust to spin orbit coupling (SOC), and are inherent to all non-centrosymmetric achiral crystal structures. In this talk I will present magneto-transport and ARPES experimental data together with DFT calculation, pointing to the existence of novel KNLs in SmAlSi. SmAlSi is a non-centrosymmetric metal that develops incommensurate spin density wave AFM order at low temperatures. I will show evidence for the symmetry-protected KNLs, as well as Weyl fermions under the broken inversion symmetry in the paramagnetic phase of SmAlSi. In the AFM state, angle-dependent quantum oscillations (AQOs) provide evidence for the Weyl points, while large AHE is observed in both the AFM and the PM states. We propose a new mechanism to explain AHE in non-FM materials, based on magnetic field-induced Weyl-nodes evolution in non-centrosymmetric Weyl semimetals. The proposed mechanism qualitatively explains the temperature dependence of the anomalous Hall conductivity (AHC) in SmAlSi.