Uranium and nickel explorer URU Metals said its Chief Executive Roger Lemaitre is stepping down, hitting its shares.URU, which has nickel projects in South Africa and uranium and gold schemes in Sweden and Canada, said Lemaitre will leave on January 10, 2014, to pursue a career opportunity with another company.Chairman David Subotic said: "The board would like to thank Roger for his considerable contribution in the positioning of URU Metals for long-term success in an extremely difficult mining climate for junior exploration companies. We wish him all the very best."Shares in URU fell 0.25p, or nearly 12%, to 1.88p by 11:02 in London.PW