It is permissible for you to lend gold in kilogram or in cash, and it should be returned to you in pounds calculated by counting or gold pieces calculated by weighing, in the same form they were received from you. There is nothing wrong with doing so, if Allah so wills. Cooperation between Muslims is required. You should just receive the gold that you lent, whether the price goes up or down. May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.