Cameron Norrie and Katie Boulter ensured Great Britain made a winning start at the United Cup with victory over hosts Australia in Perth.
Boulter then secured her nation's opening win with a match to spare by beating Ajla Tomljanovic 6-2 6-4.
GB face the United States - winners of the inaugural tournament in January - in their final Group C match on Sunday.
World number 18 Norrie, 28, dominated the decisive tie-break to earn a hard-fought win over the 12th-ranked De Minaur after two hours 23 minutes - his first victory over a top-20 opponent in his past 10 attempts.