In late August, amid a sharp plunge in the Argentine peso, global suppliers to oil giant YPF received an unwelcome surprise in their inbox. A four-page notice that dollar contracts would be paid at a set exchange rate, far weaker than the market rate. In the unsigned, undated document, obtained by Reuters, state-controlled YPF set the exchange rate at 45.19 pesos per dollar for 90 days, about a quarter below the current price, saying it faced an “unprecedented” challenge amid government fuel price caps and a brewing financial crisis.