(ShareCast News) - Tritax Big Box posted a big jump in first-half operating profit as the value of its real estate investment trust surged.Operating profit came in at £73.8m from £8.21m in the first half of 2014 as the real estate investment trust's portfolio valuation rose 203% to £1.1bn.Contracted rental income increased to £58.9m per annum from £20.8m last year and the company had a total return for the six-month period of 10.7% compared to its target of 9% per annum for the medium term.The interim dividend was lifted to 3p per share from 1.85p.The company said the profile of rent reviews across the portfolio means it is well placed to capture rental growth in the market. Tritax said it was confident of strong rental growth in the near term as the balance of occupational supply and demand should remain favourable for landlords.Chairman Richard Jewson said: "Our investment manager continues to identify and negotiate good opportunities to buy assets and create capital value enhancement for our shareholders, both at the point of purchase and through a variety of asset management initiatives."We will continue to build an increasingly diversified and high quality portfolio, as we deploy the equity and debt financing raised during the period."Jewson said the outlook for the rest of the year remains strong and the company expects to achieve its dividend target of 6p per share for the full year.