Complete miscibility amongst AV${}_3$Sb${}_5$ kagome superconductors: design of mixed A-site AV${}_3$Sb${}_5$ (A: K, Rb, Cs) alloys

In this work we explore the chemical-property phase diagram of the AV${}_3$Sb${}_5$ family through A-site alloying. We demonstrate full miscibility of the alkali-site, highlighting that the three parent compounds are the terminal ends of a single solid-solution. Using both polycrystalline and single crystal methods, we map the dependence of the two primary electronic instabilities: (1) the onset of charge density wave (CDW) order ($T_{\text{CDW}}$) and (2) the onset of superconductivity ($T_{\text{c}}$) with alkali-site composition. We show continuous trends in both $T_{\text{CDW}}$ and $T_{\text{c}}$, including a region of enhanced CDW stability in K${}_{1-x}$Cs${}_x$V${}_3$Sb${}_5$ alloys. Together, our results open new routes for chemical perturbation and exploration of the chemical-property relationships in the class of AV${}_3$Sb${}_5$ kagome superconductors.