A katana has no previous use in the Stargate Universe. They're undeniably cool, but they're not truly superior to other swords of high-quality materials (despite what certain parts of the Internet want you to think). Even if someone should own one (which is not entirely unlikely) they wouldn't have it as part of their regular uniform. If they're Japanese, it could feasibly be part of a dress uniform, but as others have said, swords are no longer part of regular field combat. Of the likely options, if your character is an officer, he or she might have a Katana on a display in his/her quarters. (S)he might even know how to use it. (everyone has hobbies after all)
That being said, a fancy weapon shouldn't be the focus of your character design. No matter how you put it, a weapon is a minor detail. What you should think more on is everything else about your character.
That being said, a fancy weapon shouldn't be the focus of your character design. No matter how you put it, a weapon is a minor detail. What you should think more on is everything else about your character.