We propose a new class of carbon allotropes obtained by combining linear sp carbon chains with sp3 bulk carbon.The structure of these crystalline carbon allotropes consists of sp chains inserted in cylindrical cavities periodically arranged in hexagonal diamond (lonsdaleite).We carry out a detailed computational analysis of the structural, electronic, and vibrational properties of a simple form in this class: a single C6 strand embedded in a nm-sized cavity.We obtain a metallic allotrope exhibiting characteristic high-frequency vibrations associated with the sp chains stretching modes, and characterized by long-time room-temperature stability.In addition, we suggest how numerous similar allotropes could be constructed within this class, that we call zayedene, all characterized by comparable metallicity and high-frequency vibrations.