What type of bonding in solid potassium

The potassium metal atoms occupying the crystal lattice that occurs is being held together by metallic boding

It is a mixture. simply put, a compound must be pure, that is, of only one chemical structure and composition. a mixture is made of different chemical substances (i.e. elements, molecules, compounds) that are not chemically bonded to each other, but instead physically grouped together, as in the case of gasoline (a homogeneous solution).