* SenseTime valued at more than $4.5 bln (Recasts and adds details of the funding): HONG KONG (Reuters) - Chinese facial recognition technology developer SenseTime Group Ltd said it has raised $620 million in a second round of funding in just two months, adding that it continued to be the world’s most valuable unicorn in artificial intelligence. The financing, which values the company at more than $4.5 billion, was led by Fidelity International, Hopu Capital, Silver Lake and Tiger Global and follows a $600 million funding round in April led by Alibaba Group.