SANTIAGO, March 19 (Reuters) - The chairman and principal shareholder of SQM, Julio Ponce, bought $4.5 million worth of shares of the Chilean fertilizer group following a stock plunge on Wednesday, as investors fretted over corporate governance issues.
Ponce investment vehicle Pampa Calichera bought 250,000 B shares in SQM on Wednesday, according to a report filed with the Santiago Stock Exchange on Thursday.
SQM's shares fell 17 percent on Wednesday to their lowest level since 2008, after representatives from Canadian stakeholder Potash Corp stepped down from the board in protest of its handling of a probe into an illicit payments scandal.
The shares fell another 2.5 percent on Thursday.
SQM shares are also among the most liquid Chilean ADRs quoted on the Nasdaq, where they have dropped some 29 percent since the start of this month.
Brokers at Miller Tabak removed their "buy" rating on the stock, and said SQM's historical valuation premium for lithium assets and corporate leadership in Chile was no longer tenable.
Nationalization or tough fines were unlikely given Chile's commitment to being investor-friendly, they said in a note to clients.
"However, a prolonged conflict with the current government will likely put future lithium concessions at a greater risk, as well as leave lingering doubts about SQM's commitment to global corporate governance standards," they added. (Reporting by Felipe Iturrieta; Writing by Rosalba O'Brien; editing by Matthew Lewis)