** South32 S32.AX rises 2.3% to A$3.51, highest since Feb. 7
** Miner logs underlying earnings of $375 mln in H1, surging 838% y/y
** Citi says co's underlying earnings beat its estimates and slightly ahead of Visible Alpha consensus estimate of $370.1 mln
** Stock rose as much as 2.9% to A$3.530 earlier in the day, marking its biggest intraday pct gain since Feb. 5
** S32 up more than 3% YTD
(Reporting by Rajasik Mukherjee in Bengaluru)
((Rajasik.Mukherjee@thomsonreuters.com))