The layered material ZrSiTe is currently extensively investigated as a nodal-line semimetal with Dirac-like band crossings protected by nonsymmorphic symmetry close to the Fermi energy. A recent infrared spectroscopy study on ZrSiTe under external pressure found anomalies in the optical response, providing hints for pressure-induced phase transitions at ≈4.1 and ≈6.5 GPa. By pressuredependent Raman spectroscopy and x-ray diffraction measurements combined with electronic band structure calculations we find indications for two pressure-induced Lifshitz transitions with major changes in the Fermi surface topology in the absence of lattice symmetry changes. These electronic phase transitions can be attributed to the enhanced interlayer interaction induced by external pressure. Our findings demonstrate the crucial role of the interlayer distance for the electronic properties of layered van der Waals topological materials.Topological materials such as topological insulators [1], Dirac [2], Weyl [3][4][5] or line-node semimetals [6,7] are of great fundamental interest due to their exotic nature of electronic phases, and thus heavily investigated nowadays. They usually exhibit extraordinary material properties, for example, high carrier mobility and unusual magnetoresistance [8][9][10]. Topological non-trivial phases often occur in layered materials with weak interlayer bonding, where the single layers behave rather as isolated two-dimensional (2D) objects, enabling the exfoliation to atomically thin 2D crystals with numerous possible applications [11][12][13][14][15]. Since the forces between the layers of such structures are usually weak, they are highly compressible perpendicular to the layers, and a dimensional crossover from 2D to 3D can be induced by external pressure. Generally, layered materials are prone to pressure-induced phenomena, and electronic topological transitions [16] are expected to be induced [17][18][19] and were suggested to occur in layered BiTeBr [20], BiTeI [21, 22], 1T-TiTe 2 [23], and the group V selenides and tellurides Bi 2 Se 3 , Bi 2 Te 3 , Sb 2 Te 3 [24-27]. "Electronic transitions" in metals were first introduced by Lifshitz in 1960 as transitions where the topology of the Fermi surface (FS) changes as a result of the continuous deformation under high external pressure [16]. Examples for pressure-induced alterations of the FS topology are the conversion of an open Fermi surface, such as * These authors contributed equally.a corrugated cylinder-type Fermi surface typical for layered materials, to a closed one, or the appearance of a new split-off region of the FS. Importantly, the changes in the Fermi surface topology during such a so-called Lifshitz transition are not related to a change in the lattice symmetry [16].In this work we find indications for two Lifshitz transitions in the layered van der Waals material ZrSiTe under external pressure, resulting from the enhanced interlayer interaction. ZrSiTe belongs to the family of compounds ZrXY (X=Si, Ge, Sn and Y =O, S, Se, Te), which are...

Polarization‐ and temperature‐dependent Raman data along with theoretical simulations are presented for the Kagome ferromagnet Fe3Sn2. Eight out of nine expected phonon modes are identified. The experimental energies compare well with those from the simulations. The analysis of the line widths indicates relatively strong phonon–phonon coupling in the range 0.1–1. The temperature‐dependent frequencies of three A1g modes show weak anomalies at ≈100 K. In contrast, the linewidths of all phonon modes follow the conventional exponential broadening up to room temperature except for the softest A1g mode, whose width exhibits a kink close to 100 K and becomes nearly constant for T>100 K. These features are indicative of a spin reorientation taking place in the temperature range above 100 K, which might arise from spin–phonon coupling. The low‐energy part of the electronic continuum in Enormalg symmetry depends strongly on temperature. The possible reasons include particle–hole excitation tracking the resistivity, a spin‐dependent gap, or spin fluctuations.

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2D angular correlation of the positron annihilation radiation (2D‐ACAR) spectra are measured for LaB6 along high‐symmetry directions and compared with first‐principles calculations based on density functional theory (DFT). This allows the modeling of the Fermi surface in terms of ellipsoid electron pockets centered at X‐points elongated along the Σ axis (Γ−M direction). The obtained structure is in agreement with quantum oscillation measurements and previous band structure calculations. For the isostructural topologically nontrivial SmB6, the similar ellipsoids are connected through necks that have significantly smaller radii in the case of LaB6. A theoretical analysis of the 2D‐ACAR spectra is also conducted for CeB6 including the on‐site repulsion U‐correction to the local density approximation (LDA+U) of the DFT. The similarities of the 2D‐ACAR spectra and the Fermi surface projections of these two compounds allow to infer that both LaB6 and CeB6 are topologically trivial correlated metals.