An Extremal N=2 Superconformal Field Theory

We provide an example of an extremal chiral $\mathcal{N}=2$ superconformal field theory at $c=24$. The construction is based on a ${\mathbb{Z}}_2$ orbifold of the theory associated to the $A_1^{24}$ Niemeier lattice. The statespace is governed by representations of the sporadic group $M_{23}$.