Among the nodal-line semimetals (NLSMs), Dirac nodal lines (DNLs) that are robust against spin-orbit coupling (SOC) have been increasingly shown to exist in three- and two-dimensional systems, but rarely occur in (quasi) one-dimensional materials. The latter can be found in two-dimensional systems with in-plane anisotropy [1], since additional crystalline symmetries such as mirror or nonsymmorphic symmetries are required to protect a nodal line band crossings [2]. A family of exfoliatable, strong in-plane anisotropic, nonmagnetic, ternary transition semimetal tellurides, Ta-based TaMTe₅ (M=Ni, Pd, Pt) [1,3,4], has recently been shown to host nodal lines with fourfold degeneracy.

Here [5] we investigated the Fermi surface and carrier mass in TaNiTe₅ and TaPtTe₅ using magnetization and magnetic torque measurements in high-quality single crystals at fields of up to 15T. Strongly pronounced de Haas-van Alphen (dHvA) oscillations can clearly be resolved, reaching to temperatures of up to 22 K for some orbits. Quantum oscillations have been tracked for fields along the three crystallographic axes, supplemented by rotation studies in the b-a and b-c planes, and were interpreted with reference to band structure calculations within density functional theory. The extracted values for the Berry phase of the obtained Fermi pockets approach Pi, demonstrating nontrivial topological electronic properties and ultra-high mobility of Dirac carriers in the conduction band.