Platinum is trading in a bear market amid prospects for higher U.S. interest rates and speculation that demand will slip for the metal used in auto pollution-control devices.

Investors have soured on platinum, used in catalytic converters that help limit pollution from diesel vehicles, as automakers introduce more electric cars and diesel loses popularity in the wake of Volkswagen AG’s emissions-cheating scandal. A strengthening dollar and the outlook for higher U.S. rates have hurt demand for precious metals as stores of value.