*2.2. Chemical Analysis*

Small pieces of single crystals of **1**–**4** verified on the diffractometer were crushed, pelletized, and carbon-coated. The chemical composition of the samples was determined using a TM 3000 scanning electron microscope equipped with an Oxford EDX spectrometer, with an acquisition time of 15 s per point in energy-dispersive mode (acceleration voltage 15 kV). The following analytical standards were used: CsBr (Cs*K*), barite (S*K*), and U3O8 (U*K*).

Analytical calculations. Compound **1**: atomic ratio from structural data Cs 1.00, U 1.00, S 1.00; found by EDX: Cs 1.03, U 1.05, S 0.92. Compound **2**: atomic ratio from structural data Cs 3.00, U 4.00, S 2.00; found by EDX: Cs 2.93, U 4.06, S 2.01. Compound **3**: atomic ratio from structural data Cs 6.00, U 2.00, S 5.00; found by EDX: Cs 5.96, U 2.07, S 4.97. Compound **4**: atomic ratio from structural data Cs 2.00, U 1.00, S 2.00; found by EDX: Cs 1.95, U 1.05, S 2.00.
