Sina (SINA) shares jumped nearly 9% in early trading Monday on reports that China e-commerce giant Alibaba is eyeing a stake in the Web portal, though neither company has yet confirmed the talks. Citing sources within Alibaba, state-owned China Business News reported the talks, saying Alibaba was considering a 15% to 20% investment in Sina, according to a report from Reuters. Reuters was unable to confirm the talks with either company. A Sina