Electronic ordering is prevalent in correlated systems, which commonly exhibit competing interactions. Here, we use x-ray diffraction to demonstrate a cascade of pressure-induced order-disorder transformations, with propagation vectors ${\mathbf{q}}_{\mathrm{CDW}}=\left(\frac{1}{2}0\frac{1}{2}\right), {\mathbf{q}}^{*}=\left(\frac{1}{3}\frac{1}{3}\frac{1}{2}\right)$, and ${\mathbf{q}}^{†}=\left(\frac{1}{3}\frac{1}{3}\frac{1}{3}\right)$, in the kagome metal FeGe. In the pressure interval between $4<p<10$ GPa, ${\mathbf{q}}_{\mathrm{CDW}}$ and ${\mathbf{q}}^{*}$ coexist and the spatial extent of the $\sqrt{3}\times \sqrt{3}$ order is nearly long range at $\sim 15$ GPa, $\sim 30$ unit cells. Above $\sim 25$ GPa, the periodic lattice distortion has a propagation wave vector of ${\mathbf{q}}^{†}=\left(\frac{1}{3}\frac{1}{3}\frac{1}{3}\right)$ at room temperature. The cascade of phase transitions is captured by the Ising model of frustrated triangular lattices and modeled by Monte Carlo simulations based on the dimerization of trigonal ${\mathrm{Ge}}_1$. The pressure dependence of the integrated intensities and correlation lengths of ${\mathbf{q}}_{\mathrm{CDW}}, {\mathbf{q}}^{*}$, and ${\mathbf{q}}^{†}$ demonstrating a competition between the $2\times 2$ and $\sqrt{3}\times \sqrt{3}$ phases prove the tunability of order-disorder phase transitions under pressure and the rich landscape of metastable/fragile phases of FeGe.

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• Charge density waves
• Critical phenomena
• Order parameters
• Kagome metal
• Monte Carlo methods
• X-ray diffraction