FRANKFURT (Reuters) - Shares in Germany's SGL Group were down 14.5% in early trade after the maker of carbon fibres for auto parts said its chief executive would quit and its earnings prospects for the year had worsened.The company, in which BMW investor Susanne Klatten owns 28%, said late on Wednesday it expected adjusted operating profit of about 10 million euros (9 million pounds), down from previous guidance of about 65 million.Business in July at its Composites – Fibres & Materials..