Quasiparticles with the Dirac spectrum arise in a number of materials. Well-known examples are graphene, topological insulators, Dirac semimetals. More recently, it has been found that there are also materials in which the vertices of the Dirac cone are not at one or more points of the Brillouin zone, but form a line [1]. A feature of nodal-line Dirac semimetals is the much higher density of Dirac states than in materials with Dirac points, which allows us to hope for a more vivid manifestation of the properties due to Dirac fermions.
  ARPES study supported by first-principle calculations show that InBi is a Dirac semimetal in which the vertices of the Dirac cone form the lines in the momentum space along the directions MA and XR of the Brillouin zone, i.e. in the directions along the c axis [2]. Earlier studies of magnetoresistance in InBi indicate the presence of an extremely large positive transverse quadratic magnetoresistance, which exceeds 2 orders of magnitude and does not saturate in high magnetic fields [3]. The absence of saturation and its anomalously high value are associated with the equality of the concentrations of electrons and holes whose mobility at helium temperatures exceeds 10⁴ cm²/V·s [3].   
  In this work, we present the results of high precision measurements of the transverse magnetoresistance in InBi. These enable us to distinguish features which were not observed previously. In particular, we found that the dependence of the resistance R on  magnetic field B does not follow the simple quadratic law  R(B) = R₀ + bB². Namely, at B < 0.1 T, it is characterized by high curvature,  at B > 1 T it approaches a quadratic law with a curvature several times smaller, and in the intermediate region it is described by the sum of linear and quadratic contributions. The observed deviation from the quadratic dependence corresponds to a linear contribution, which is expected for nodal-line Dirac semimetals [4]. We also proposed a simple formula

                                                           R(B) = R₀+R₁(1+η²B²)^1/2+bB²,            
describing all the detected features of the magnetoresistance of the nodal-line Dirac semimetal InBi within the experimental accuracy of a few percent.

[1] A. A. Burkov, M. D. Hook, and L. Balents, Phys. Rev. B 84, 235126 (2011).
       [2] S.A. Ekahana, Sh.-Ch. Wu, J. Jiang, K. Okawa, D. Prabhakaran, Ch.-C. Hwang, S.-K. Mo, T. Sasagawa, C. Felser, B. Yan, Zh. Liu and Yu. Chen, New J. Phys. 19, 065007 (2017).
       [3] K. Okawa, M. Kanou, H. Namiki, and T. Sasagawa Phys. Rev. Materials 2, 124201 (2018).
       [4] H. Yang and F. Wang, arXiv:1908.01625.

S.V. Zaitsev-Zotov and I.A. Cohn
JETP Letters 111, issue 1 (2020)