(Reuters) - Investment firm Sixth Street Partners has sued Dyal Capital Partners as it looks to block the asset manager’s proposed merger with direct lender Owl Rock Capital and their deal to go public through an acquisition by a blank-check company. Special purpose acquisition company (SPAC) Altimar Acquisition Corp on Tuesday revealed the lawsuit in a filing bit.ly/3psmvgC, which contained a letter from Dyal Capital Partners. The deal with the SPAC, valued at $12.5 billion, was announced in December last year. Sixth Street claimed the merger violated a non-compete clause signed with Dyal, Axios reported citing sources. (bit.ly/2LWIIpF) The lawsuit will not be made public until Wednesday, the report from Axios added. Dyal Capital Partners, the Neuberger Berman Group unit that buys minority stakes in hedge and private equity fund firms, owns a minority stake in Sixth Street since 2017. Altimar went public in a $250 million IPO in October last year. (This story corrects paragraph 2 to remove reference to Altimar Acquisition Corp challenging Sixth Street’s lawsuit)