How about a "Small Sword" It is what a rapier evolved into when people started to to realize how clumsy a rapier could be. Go on youtube and look a film called "the Dualist" to see a short sword in action. Also look into Filipino or south east Asian bladed weapons if you want to get away from the Katana, which I find to be pretty generic.
When you say alien metal I assume you mean some kind of fantasy metal and not some type of sci-fi material. Because if this is a futuristic setting, well, you are right that katanas outside of their historical setting are beginning to be over used and overrated, but I believe swords in a sci-fi setting are a massive faux pas unless there are some strong justifications for it. When ever I see some badass warrior wielding a sword in sci-fi I'm instantly reminded of this
