This is what you're looking for:
http://www.highend3d.com/softimage/tools/
Scroll down until you find Photoshop Softimage Pic Image Reader v1.1.
Place the file (soft.8bi) into: C:Program FilesAdobePhotoshop 6.0Plug-InsFile Formats.
In Photoshop 7 the PIC format plug-in is now included with the software.
BTW: You can output different formats than PIC from XSI. Just check the Render Options, in the Output tab....
Hope this helps
Salutations - Cheers
Bernard Lebel