primary key and unique index

Hi all,

I am migrating fromMySQL to Postgresql 9.6.

In MySQL a "show create table" gives me :
...
PRIMARY KEY (`ID`,`CountryCode`,`LanguageCode`),
UNIQUE KEY `unique_my table_4` (`ID`,`CountryCode`,`LanguageCode`),
...

So, In PostgreSQL, does it make sense to create a primary key AND a unique
index based on the same columns?
Is PostgreSQL smart enough to use the unique index created for the primary
key.

I know PostgreSQL can be based on a unique index to create a primary key
but I also know it is possible to create several indexes on the same
columns with the same order.

Thanks

Thomas