  In the present paper we describe new component of the Gieseker-Maruyama
moduli space $\mathcal{M}(14)$ of coherent semistable rank-2 sheaves with Chern
classes $c_1=0, \ c_2=14, \ c_3=0$ on $\mathbb{P}^{3}$ which is generically
non-reduced. The construction of this component is based on the technique of
elementary transformations of sheaves and famous Mumford's example of a
non-reduced component of the Hilbert scheme of smooth space curves of degree 14
and genus 24.
