Search Term 2 field in vendor master

In vendor master (XK03), there is Search Term 1 and Search Term 2 fields. For some vendors, we have put values in both fields. However, when we try to do a 'search' for the vendor, it does not look into Search Term 2.

Does anybody know where we can 'activate' this field? I tried to enter it as a matchcode, but the system does not allow it.

thank you.