Single-crystal X-ray diffraction. To obtain single crystals of D-U hyd, 15 mg of a dry ground equimolar mixture of D and U was dissolved in 5 mL of methanol. Singlecrystals were grown after solvent evaporation at room temperature. Single crystal measurements were performed on an Oxford Diffraction Xcalibur Nova R (microfocus Cu tube) equipped with an Oxford Instruments CryoJet liquid nitrogen cooling device. Program package CrysAlis P RO 35 was used for data reduction and numerical absorption correction. The structures was solved using SHELXS97 and refined with SHELXL-2017. The model was refined using the full-matrix least-squares refinement; all non-hydrogen atoms were refined anisotropically. Hydrogen atoms were located in a difference Fourier map and refined as a mixture of free-restrained and riding entities. The co-crystallized water molecule (O3) is disordered over two positions (designated as A and B) with respective occupancies of 63% and 37%. Molecular geometry calculations were performed by PLATON and molecular graphics were prepared using ORTEP-3, and Mercury. Crystallographic and refinement data for D-U hyd is shown in Figure . The structure has been deposited in the Cambridge Crystallographic Data Centre (CCDC) as no. 2059340. 3D electron diffraction. ED measurements for D-U anhyd were collected using the Rigaku XtaLAB Synergy-ED, equipped with a Rigaku HyPix-ED detector optimized for operation in the continuous rotation 3D-ED experimental setup. Data acquisition was performed at ambient temperature under high vacuum with an electron wavelength of 0.0251 Å. The instrument was operated and the diffraction data were processed in the program CrysAlis P RO . A multi-scan absorption correction was performed using spherical harmonics implemented in SCALE3 ABSPACK scaling algorithm in CrysAlis P RO . The structure was solved using ShelXT, and subsequently, refined with kinematical approximation using ShelXL in the crystallographic program suite Olex2. By merging data of three indi-vidual grains/datasets, completeness of 96.2% up to a resolution of 0.80 Å was achieved.