The mining sector is given a lift by an improvement in metals prices, which fell back yesterday.Among the risers is Rio Tinto, which said it is in talks with several of its iron ore customers about moving to quarterly pricing of iron ore contracts.Shares in US based bio-refining company GTL shot ahead after it said trading in the second half "substantially exceeded" first half, while full year figures should be "significantly" ahead of market expectations.But the alternative energy sector is lower overall, with China Biodiesel International the heaviest faller.Shares in D1 Oils, which continues to be 'actively engaged' in a series of discussions with third parties regarding the provision of material levels of equity finance which may include the possibility of an offer being made for the biofuels group, are flat.Top performing sectors so far todayAutomobiles & Parts 3,292.00 +2.03%Electricity 6,527.47 +1.91%Mining 24,865.14 +1.59%Chemicals 5,309.45 +1.45%Travel & Leisure 4,848.52 +1.43%Bottom performing sectors so far todayAlternative Energy 6,171.54 -0.32%Mobile Telecommunications 3,423.89 -0.27%Financial Services 5,242.57 -0.26%Real Estate Investment & Services 1,597.14 -0.12%Pharmaceuticals & Biotechnology 8,869.37 -0.05%