Lee-extremal self-dual codes over F2+uF2F2+uF2 of lengths 23 and 24

We completely classify the Lee-extremal self-dual codes over F2+uF2F2+uF2 of lengths 23 and 24 with a nontrivial automorphism of odd order. In particular, we show that there is no Lee-extremal self-dual code of length 23 with a nontrivial automorphism of odd order, there are 41 inequivalent Lee-extremal Type I codes of length 24 with a nontrivial automorphism of odd order and there exists one Lee-extremal Type II code of length 24 with a nontrivial automorphism of odd order, up to equivalence. Moreover, Lee-extremal Type II codes of length 24 have an automorphism of order 3.