FYI, it has been suggested by a number of nuclear physicists at a site called 'MadSci' that "unmatter" is a nonsense concept as relates to physics--see this link:
http://www.google.com/u/MadSciNet?q=unmatter&sa=Search&domains=madsci.org&sitesearch=madsci.org
But I find this to be a strange point of view, rather narrow minded. For example, it is well known that pions meet the definition of matter + antimatter = unmatter (e.g., the (ud^, u^d, etc. where ^ = antimatter). Also, the pentaquark (qqqqq^), which is a type of unmatter, appears to exist when looked for at low energy reactions--see this link for updated pentaquark controversy (pro-con as of 2005).
http://www.phy.ohiou.edu/~hicks/thplus.htm
Plus, the recent paper "Antibaryons in Nuclei", published in Phys. Rev. C (71), 2005 confirms the existence of antimatter bound within matter, thus forming unmatter. I suspect that many other forms of "unmatter" exist, but I would appreciate hearing from others on this topic.