Those are BE catalog files. To reduce the size of your catalogs, you can reduce the truncate period and the removal period. These are found under Tools, Options, Catalogs. Bear in mind that as you decrease these, you increase the likelihood of having to catalog a tape before you can restore from it.
An alternative is to move the catalog folder to another drive with more available space. http://seer.entsupport.symantec.com/docs/264680.htm
Mark