It's obviously intended to be a play on a Katana (with Auron's obvious Ronin basis) but a really exaggerated one. To be honest, it makes me think of a Zanbatou or a Nagamaki only with the length of the components reversed: Instead of a really long handle with a Katana-like blade, it has a Katana-like handle with a really long -- and wide -- blade.

But, no, it's definitely not a standard Katana.