Clearwire Corporation (NASDAQ:CLWR)’s biggest shareholders still oppose the Sprint Nextel Corporation (NYSE:S) buyout of the company, according to documents filed with the U.S. Securities and Exchange Commission this week. Not long after the documents were posted, Clearwire shares did an about-face and started rising—as much as 3 percent at the time of this writing after sagging all week.

Sprint Clearwire

The documents indicate that several of Clearwire’s biggest shareholders, including Mount Kellett Capital Management LP and Highside Capital Management, L.P., are in opposition of the proposed merger and have decided to look for better offers. They list the entire group that’s in opposition to the merger as owning (together) about 18.2 percent of the company’s total outstanding shares.

The documents have a filing date of May 1, and Clearwire Corporation (NASDAQ:CLWR) said that on that day, it agreed to enter into discussions collectively with Sprint Nextel Corporation (NYSE:S) and its affiliates and “other interested parties, including DISH Network” Corp (NASDAQ:DISH) and its affiliates.

Clearwire Keeping Its Options Open

Clearwire had said in February that it still wanted to talk to both Sprint and DISH Network. In January the company asked Sprint Nextel to up its bid after DISH submitted its unsolicited bid. However, Clearwire continued to draw on pre-merger financing from Sprint Nextel, dipping into the financing yet again in April, which may have led investors to believe that Clearwire would accept Sprint Nextel’s offer.

As it stands, the current offer from Sprint Nextel Corporation (NYSE:S) is $2.97 per share for Clearwire Corporation (NASDAQ:CLWR) shareholders. The SEC documentation shows that Mount Kellett, Highside and the other opposing shareholders believe that this price is too low. It also says that the opposing shareholders entered into an agreement to discuss “with relevant and interested parties to seek to maximize shareholder value.”

Clearwire Corporation (NASDAQ:CLWR) reported in the documents that it will hold a shareholder meeting May 21, and a vote on the merger will be held.