** South32 S32.AX falls more than 4% so far this week
** UBS cuts PT to A$4.50/share; maintains "buy"
** Trims net asset value estimate by $2.2 billion to $3.4 billion for co's mining project Hermosa in Tucson, Arizona
** Higher capex, delayed operations at Hermosa mean investors will have to wait until FY29-FY30 before co generates strong cash returns
** Says "risk-reward" remains attractive due to commodity mix
** S32 rises as much as 3% to A$4.15; marks steepest intraday pct rise since April 8
** YTD, stock up 40%
(Reporting by Anjali Singh in Bengaluru)
((anjali.singh2@thomsonreuters.com;))