Anomalous anisotropic magnetotransport behavior mediated by Fermi surface reconstruction in topological nodal line TiB2 single crystals

Transition metal diborides (MB${}_2$), characterized by their simple crystal lattice structure and wide linear dispersion range, serve as an ideal system for exploring novel topological states and anomalous physical properties. In this study, we report a temperature-induced Fermi surface reconstruction at around 100 K and the anomalous magnetotransport behaviors mediated by it in nodal line semimetal TiB${}_2$ single crystals. The experimental evidence for the Fermi surface reconstruction comes from the following aspects: (i) a noticeable dip in the temperature-dependent Seebeck coefficient; (ii) a breakdown of the Kohler’s rule; (iii) abnormal changes of hole carriers at around 100 K; (iv) the sharp change of twofold symmetry in the angle-dependent magnetoresistance (ADMR) patterns. Through such a Fermi surface reconstruction, the anisotropic magnetotransport behavior of TiB${}_2$ exhibits significant changes. At low temperatures, TiB${}_2$ exhibits field orientation-dependent superlinear unsaturated MR, while at high temperatures it can transform to linear MR or sublinear MR depending on the direction of magnetic field. Finally, the possible origin of the Fermi surface was discussed. This work reveals the presence of Fermi surface reconstruction and provide a suitable platform for exploring the relationship between Fermi surface topology and anomalous magnetotransport phenomenon in topological semimetals.