Structural, vibrational, and electrical transport properties of nodal-line semimetal candidate CaCdGe under high pressure

Nodal-line semimetals provide the opportunity to explore exotic properties owing to their nontrivial band structures. Here, the structural and electronic properties of nodal-line semimetal candidate CaCdGe were systematically investigated under pressure up to 53.3 GPa through synchrotron x-ray diffraction, Raman scattering, electrical transport measurements, and theoretical calculations. Upon compression, although no trace of evident structural transition is detected, a maximum value of lattice ratio c/a and abnormal changes in bond angles around PC & SIM; 12.5 GPa are observed from our x-ray diffraction data. Meanwhile, a new Raman peak is observed in the vicinity of PC. Furthermore, the resistance parameters (n, A, and OR) all show the abrupt changes above PC. Since the electronic topological transition is absent within 30.0 GPa based on band structure calculations, our results may demonstrate the occurrence of a subtle isostructural transition around PC in pressurized CaCdGe, due to the distortion of CdGe4 tetrahedra.