On Linux, creating a fake file using

perl -e 'print "\x00\x06\xde\xad\xbe\xef";' > foo

and running file foo yields

foo: TTComp archive data

Then it's easy: http://fileformats.archiveteam.org/wiki/TTComp_archive

On Linux, creating a fake file using

perl -e 'print "\x00\x06\xde\xad\xbe\xef";' > foo

and running file foo yields

foo: TTComp archive data

Then it's easy: http://fileformats.archiveteam.org/wiki/TTComp_archive which says that it used the early PKWARE "implode" algorithm

DCL Implode is not the same format as ZIP's old "implode" compression method (#6). It is unfortunate that there are two formats named "implode" associated with the same company. It can be used in ZIP, as compression method #10, but support for this is limited.

The terms "blast" and "explode" are sometimes used in association with this format.

There are decoders for it, for example this one written in Go.