(August 10, 2021, 2:22 PM EDT) -- NEW YORK — Two investors and their companies who were awarded more than $500 million against the Republic of Kazakhstan in 2013 for an oil and gas field investment expropriation sent Kazakhstan a letter on Aug. 5 stating that they plan to bring a new arbitral claim against it for allegedly breaching the Energy Charter Treaty (ECT) by engaging in “frivolous” litigation opposing enforcement of the award unless a settlement can be reached within three months....