Pressure evolution of electronic and crystal structure of noncentrosymmetric EuCoGe3

We report on the pressure evolution of the electronic and crystal structures of the noncentrosymmetric antiferromagnet ${\mathrm{EuCoGe}}_{3}$. Using a diamond anvil cell, we performed high pressure fluorescence detected near-edge x-ray absorption spectroscopy at the Eu ${L}_{3}$, Co $K$, and Ge $K$ edges and synchrotron powder x-ray diffraction. In the Eu ${L}_{3}$ spectrum, both divalent and trivalent Eu peaks are observed from the lowest pressure measurement ($\ensuremath{\sim}2$ GPa). By increasing pressure, the relative intensity of the trivalent Eu peak increases, and an average Eu valence continuously increases from 2.2 at 2 GPa to 2.31 at $\ensuremath{\sim}50$ GPa. On the other hand, no discernible changes are observed in the Co $K$ and Ge $K$ spectra as a function of pressure. With the increase in pressure, lattice parameters continuously decrease without changing $I4mm$ symmetry. Our study revealed a robust divalent Eu state and an unchanged crystal symmetry of ${\mathrm{EuCoGe}}_{3}$ against pressure.