# Quadratic to linear magnetoresistance tuning in TmB4

## TL;DR

This study demonstrates that the magnetoresistance in TmB4 can be tuned from quadratic to linear by adjusting the magnetic field direction, revealing anisotropic Fermi surface effects and potential quantum mechanical origins.

## Contribution

It reports the first observation of tunable linear magnetoresistance in a good metal crystal, linked to anisotropic Fermi surface topology and quantum effects.

## Key findings

- Magnetoresistance in TmB4 can be tuned from quadratic to linear.
- Linear MR is temperature-independent, indicating quantum origin.
- Anisotropic Fermi surface explains the LMR in this good metal.

## Abstract

The change of a material's electrical resistance (R) in response to an external magnetic field (B) provides subtle information for the characterization of its electronic properties and has found applications in sensor and storage related technologies. In good metals, Boltzmann's theory predicts a quadratic growth in magnetoresistance (MR) at low B, and saturation at high fields. On the other hand, a number of nonmagnetic materials with weak electronic correlation and low carrier concentration for metallicity, such as inhomogeneous conductors, semimetals, narrow gap semiconductors and topological insulators, two-dimensional electron gas (2DEG) show positive, non-saturating linear magnetoresistance (LMR). However, observation of LMR in single crystals of a good metal is rare. Here we present low-temperature, angle dependent magnetotransport in single crystals of the antiferromagnetic metal, TmB4. We observe large, positive and anisotropic MR(B), which can be tuned from quadratic to linear by changing the direction of the applied field. In view of the fact that isotropic, single crystalline metals with large Fermi surface (FS) are not expected to exhibit LMR, we attribute our observations to the anisotropic FS topology of TmB4. Furthermore, the linear MR is found to be temperature-independent, suggestive of quantum mechanical origin.