Ionic liquids and deep eutectic solvents are of growing interest as solvents for the resource‐efficient synthesis of inorganic materials. This Review covers chemical reactions of various deep eutectic solvents and types of ionic liquids, including metal‐containing ionic liquids, [BF₄]⁻‐ or [PF₆]⁻‐based ionic liquids, basic ionic liquids, and chalcogen‐containing ionic liquids. Cases in which cations, anions, or both are incorporated into the final products are also included. The purpose of this Review is to raise caution about the chemical reactivity of ionic liquids and deep eutectic solvents and to establish a guide for their proper use.

Combinations of nontrivial band topology and long-range magnetic order hold promise for realizations of novel spintronic phenomena, such as the quantum anomalous Hall effect and the topological magnetoelectric effect. Following theoretical advances, material candidates are emerging. Yet, so far a compound that combines a band-inverted electronic structure with an intrinsic net magnetization remains unrealized. ${\mathrm{MnBi}}_2{\mathrm{Te}}_4$ has been established as the first antiferromagnetic topological insulator and constitutes the progenitor of a modular $({\mathrm{Bi}}_2{\mathrm{Te}}_3{)}_n({\mathrm{MnBi}}_2{\mathrm{Te}}_4)$ series. Here, for $n=1$, we confirm a nonstoichiometric composition proximate to ${\mathrm{MnBi}}_4{\mathrm{Te}}_7$. We establish an antiferromagnetic state below 13 K followed by a state with a net magnetization and ferromagnetic-like hysteresis below 5 K. Angle-resolved photoemission experiments and density-functional calculations reveal a topologically nontrivial surface state on the ${\mathrm{MnBi}}_4{\mathrm{Te}}_7(0001)$ surface, analogous to the nonmagnetic parent compound ${\mathrm{Bi}}_2{\mathrm{Te}}_3$. Our results establish ${\mathrm{MnBi}}_4{\mathrm{Te}}_7$ as the first band-inverted compound with intrinsic net magnetization providing a versatile platform for the realization of magnetic topological states of matter.