We examine the structural, vibrational, and transport properties of ${\mathrm{EuAg}}_4{\mathrm{As}}_2$ single crystals under pressures up to 28.8–41.8 GPa, aiming to trace the evolution of the structural distortion near $T_{\mathrm{S}}\sim 130\mathrm{K}$ and the two magnetic transitions at $T_{\mathrm{N}1}\sim 15\mathrm{K}$ and $T_{\mathrm{N}2}\sim 9\mathrm{K}$. Under ambient conditions, a Raman-active phonon mode centered at $\sim 157\mathrm{c}{\mathrm{m}}^{-1}$ is observed and identified as having $A_{1g}$ symmetry, and its temperature evolution shows no discernible anomaly across these three transitions. Under pressure, combined synchrotron x-ray diffraction and Raman measurements reveal two structural distortions at $P_{\mathrm{C}1}\sim 7$ GPa and $P_{\mathrm{C}2}\sim 17$ GPa. Structural refinements and bond-valence-sum analysis suggest that these transitions mainly involve successive discontinuous modifications of the Ag-As tetrahedra, without changing the average crystal symmetry. Distinct transport and magnetic responses accompany these structural distortions: For $P<P_{\mathrm{C}1}, T_{\mathrm{S}}$ increases while its resistivity anomaly is suppressed and $T_{\mathrm{N}1}$ and $T_{\mathrm{N}2}$ gradually increases; for $P_{\mathrm{C}1}<P<P_{\mathrm{C}1}$, high-temperature ferromagneticlike and low-temperature antiferromagneticlike states emerge; and for $P>P_{\mathrm{C}2}$, the resistivity becomes metalliclike, with only a faint broad kink and very weak magnetoresistance comparable to that of traditional metals.

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• Magnetic phase transitions
• Pressure effects
• Structural phase transition
• Rare-earth magnetic materials
• Raman spectroscopy
• Resistivity measurements
• X-ray powder diffraction