To understand structural changes associated with the incorporation of Co into LLZO SCXRD on small pieces of the individual samples has been performed. Details on refinement and fitting strategies are given in Supplementary Note 1 and refined site occupation factors are given in Tables and. The full set of structural parameters is deposited as crystallographic information Files (CIF) in the SI and under CSD numbers #2235925 -2235930. LLZO-p shows cubic symmetry, space group 𝐼4 & 3𝑑 . The super-structure, obeying 𝐼𝑎3 & 𝑑 symmetry is weakly developed. As found in previous studies, Ga 3+ orders onto the tetrahedral 12a site. Under the assumption of similar vacancy concentrations on both tetrahedral sites, the refined Ga 3+ content is ~ 0.08 atoms per formula, this indeed is very close to the boarder of chemically induced 𝐼𝑎3 & 𝑑 to 𝐼4 & 3𝑑 symmetry change, proposed by some of us. Intensity data of pieces of LLZO-o single-crystal slabs also show SG 𝐼4 & 3𝑑, whereby Bragg peaks obeying 𝐼𝑎3 & 𝑑 symmetry, are much more intense and the 𝐼4 & 3𝑑 superstructure is more developed compared to LLZO-p (see Figure ). The slight increase in electron density at the tetrahedral 12a site, while the one at 12b and 48e remains constant, suggests that Co preferentially occupies the 12a site and stabilizes in acentric symmetry 𝐼4 & 3𝑑.