Hi Will,
Rollei Infrared 400S (that is Agfa-Gevaert Aviphot Pan 400) is available as 4x5" sheet film.
This film looks a bit similar to Scala 200X as a BW slide, if you expose it just like a normal film (without red or infrared filter).
The difference between both films: Red is darker with Scala, and Scala has a bit finer grain (which is nearly irrelevant in 4x5").
Rollei 400S can be developed in the Scala Process.
Besides, lots of 'conventional' BW sheet films can be reversal developed. You can do it at home, just like normal BW negative processing.
Here are two methods of doing it:
http://home.snafu.de/jens.osbahr/photography/reversal_processing/osbahr_reversal.pdf
http://www.ilfordphoto.com/Webfiles/20114271220441194.pdf
Sheet film slides, BW and Color, are really breathtaking.
Cheers, Jan