[gilleain]

So a physics stack exchange question (https://physics.stackexchange.com/questions/221440/space-gro...) led me to a paper (https://nvlpubs.nist.gov/nistpubs/jres/107/4/j74mig.pdf) that discusses the difference between C-centered (base-centered) cells and I-centered (body centered cells).

Long story short, I think I2/c is conventionally C2/c - https://www.globalsino.com/EM/page1891.html