Either open the assembly in SEEC onto a clean cache, and the provide a copy of your cache folder content or use Teamcenter PLM/XML export rules to export the files.
IMHO, of the two methods, the open in SEEC cache will most probably give you the best results.
We use teamcenter to do this with the PLMXML function - open the assembly in Structure Manager then Tools>Export>To PLMXML and we use transfer mode "ConfiguredDataFilesExportDefault" - I think this is standard but may be custom for us.
The difference is that downloading it into a clean cache will also pull down any other parts, not in the assembly, that the parts in the assembly are linked to (so that SE can fully define them in memory). There's pros and cons to this, in our case we're sending the parts to fabricators so they're only interested in the geometry as last saved, they dont need to edit or update the parts. Other misc. parts would confuse things and mess up their BOM.
Thanks! I needed to be able to edit the linked sub-assemblies so the cache folder method works just fine.