These two words, amiable and amicable, should be carefully distinguished.
Amiable is used to describe people or expressions and means “appearing pleasant, agreeable, and friendly”: an amiable mood, an amiable smile.
Amicable is used to describe arrangements or agreements and means “showing friendly goodwill”: The two sides reached an amicable agreement. They settled their differences in an amicable manner.
Source: The Penguin Wordmaster Dictionary, Martin Manser and Nigel Turton, eds., 1987.