OLKCD or OLKB8 subdirectories of Temporary Internet Files

At my company many of us have a hidden subdirectory named one of the above.
We cannot access the files via Windows Explorer, but can see them when we get
an attachment via email. It seems to be the default for saving attachments.

I have found a way to get there by doing a search on the drive and using the
shortcut to get to the directory. I have deleted those files, all of which
came through my email and were accidentally saved to that directory.

But I'm suspicious. What is it? Why is it in temporary internet files?
Why can't I see it through Windows Explorer? Why, when I do a search on the
Internet, I can find other references to that subdirectory? Is it something
created by maliciousware?
.