** Chilwa Minerals CHW.AX rises as much as 4.5% to A$0.983, highest since February 20

** Stock posts biggest intraday pct gain since February 13

** Co says Niobium discovery confirmed at Mmpyupyu Target, within its Lake Chilwa critical minerals project in southern Malawi

** YTD, CHW up 4.8%

(Reporting by Roshan Thomas in Bengaluru)

((Roshan.Thomas@thomsonreuters.com;))