SEOUL, Jan 15 (Reuters) - South Korea’s central bank kept its policy rate unchanged on Friday, as a partial recovery in Asia’s fourth-largest economy allowed policymakers to stay on the sidelines. The Bank of Korea, as expected by all 28 analysts in a Reuters poll, kept the base rate steady at a historic low of 0.5%. (Reporting by Cynthia Kim, Joori Roh; Editing by Sam Holmes and Tom Hogue)