I've never seen anything like this, except for files which were created manually. What's the name of the file? Could the size be associated with anything? Please attach a screenshot of the datastore browser window.
You can can delete the files.
I've got similar files from a 3.x to 4.x migration and some manually cloning procedures.
I have had a similar problem. In my environment the reason for this behaviour was Windows and Unix admins deleting VM's. I have created custom roles for Windows and Unix admins and had to set this privilege (Datastore -> Low level file operations) for the role otherwise it would create this tmp file when deleting a VM. It is not a problem when using a user with Administrator privileges.
I don't know if this is the solution for your problem?
We had a lot of vms being deployed from template & then being deleted, BUT there were many folders that were empty except for the imcXXXX.tmp so I decided to investigate.
The file imcXXXX.tmp exists after cloning/deploying vm from template and choosing to customize it.
The temp file is created, then after the vm is powered on the file is run inside the vm, customizing it, and the .tmp file in the home folder is removed automatically.
If you never power on the vm but then delete it from disk, that file will still remain in the folder. You have to delete it manually afterwards.
A bit more about cutomization can be found here: