There exists no self-dual [24,12,10] code over F5
  Self-dual codes over F5 exist for all even lengths. The smallest length for which the largest minimum weight among self-dual codes has not been determined is 24, and the largest minimum weight is either 9 or 10. In this note, we show that there exists no self-dual [24,12,10] code over F5, using the classification of 24-dimensional odd unimodular lattices due to Borcherds. 
Masaaki Harada and Akihiro Munemasa