Kospi Jumps 6% as SK Hynix Buyback and Lower US Yields Boost AI Stocks

SK Hynix jumped more than 12% on Thursday and Samsung Electronics gained about 8.9%, helping South Korea’s Kospi surge 6.13% as a record share buyback and falling US Treasury yields revived demand for AI-related stocks.

The rebound followed another volatile stretch for Korean equities, where semiconductor shares have become increasingly sensitive to both AI spending expectations and movements in global bond markets.

SK Hynix Announces Record $28.8B Buyback

SK Hynix provided the strongest company-specific catalyst after announcing a 40 trillion won, or roughly $28.8 billion, share repurchase and cancellation program.

The buyback covers about 24.07 million shares, equal to roughly 3.3% of issued stock, with purchases expected to run for around three months. All acquired shares will be cancelled.

That reduction in the share count can support earnings per share and return on equity, giving the stock additional structural support.

The announcement also helped sentiment recover after SK Hynix recently suffered a sharp decline following its latest earnings, when high expectations around AI memory demand overshadowed otherwise strong profit growth.

Falling Treasury Yields Lift the Broader AI Trade

The buyback does not fully explain why Samsung rose almost 9% alongside SK Hynix.

US long-term Treasury yields fell Wednesday after the Treasury Department said it would double some liquidity-support buybacks of long-dated government debt from $2 billion to at least $4 billion per operation.

The 30-year yield dropped by roughly 10 basis points to around 5.19%, according to Reuters.

Lower yields tend to support growth stocks because they reduce the discount rate applied to future earnings. The effect is particularly important for AI-related companies whose valuations depend heavily on expectations for years of data-center investment.

Samsung and SK Hynix are central suppliers to that cycle through advanced memory and high-bandwidth memory chips. Easier financing conditions can therefore improve confidence that hyperscalers will continue funding expensive AI infrastructure.

That relationship has become increasingly important as the broader AI memory trade faces pressure from high valuations and rising borrowing costs.

KB Securities strategist Lee Eun-taek has warned that a US 10-year Treasury yield near 5% to 5.3% could threaten the AI investment cycle by making data-center financing less attractive.

Thursday’s rally therefore reflected two forces at once: a major shareholder-return catalyst for SK Hynix and broader relief from falling bond yields, which lifted Samsung and the wider Korean market.