I have a tabularx-table with a lot of SI values. For this, I wanted to define a new column type u which places the contents of the column into a \SI{XXX}{cm} expression.
\newcolumntype{u}{>{\SI\begingroup}{X}<{\endgroup{cm}}}
Using this in a tabularx-table throws me an "Illegal pream token X" and "invalid-token-in-number" exception. Replacing X with c leaves me with only the "invalid-token"-exception. What can I do to make this work?