Is this a steam code or otherwise compatible with the steam version of XCOM?

I bought this retail version and it has a steam code in a small booklet inside. It works with with my steam version of XCOM Enemy Unknown which is required to play Enemy Within. Steam treats this expansion as an add-on or dlc, therefore Enemy Within won't show up in the steam game library list.

MXN$481^.39

VAT-Inclusive Price

MXN$709.11 Shipping

Limit 99999 per customer.

Ships from United States.

Add to wish list

Sold by Newegg

Shipped by Newegg

Main image of XCOM: Enemy Within - (Requires Enemy Unknown)

Alt view image 2 of 9 - XCOM: Enemy Within - (Requires Enemy Unknown)

Alt view image 3 of 9 - XCOM: Enemy Within - (Requires Enemy Unknown)

Alt view image 4 of 9 - XCOM: Enemy Within - (Requires Enemy Unknown)

Alt view image 5 of 9 - XCOM: Enemy Within - (Requires Enemy Unknown)

Alt view image 6 of 9 - XCOM: Enemy Within - (Requires Enemy Unknown)

Alt view image 7 of 9 - XCOM: Enemy Within - (Requires Enemy Unknown)

Alt view image 8 of 9 - XCOM: Enemy Within - (Requires Enemy Unknown)

Alt view image 9 of 9 - XCOM: Enemy Within - (Requires Enemy Unknown)

Shop All 2K GAMES Products

XCOM: Enemy Within - (Requires Enemy Unknown)

(4) Write a Review

2K Games
M - Mature
Genre Strategy

Overview

Specs

Reviews (4)

XCOM: Enemy Within is the expansion to the 2012 Game of the Year strategy game XCOM: Enemy Unknown. Enemy Within adds an incredible array of new abilities, upgrades, and weapons to combat new enemy and alien threats. This expansion pack also introduces new maps, new tactical and strategic gameplay, and new multiplayer content to provide a fresh new gameplay experience.

NOTE: Requires XCOM: Enemy Unknown to play

New Soldier AbilitiesResearch new alien technology to advance the capabilities of your operatives.
New Weapons and EquipmentGive your operatives an extra tactical edge with new projects from your engineering team and the Foundry.
New Enemy ThreatsAdopt new tactics to counter the threats from two new alien classes, including the Mechtoid.
New Strategic ResourceA valuable new alien resource, known as MELD, has been released onto the landscape providing access to new research and upgrades.
New Tactical Challenges and MapsNew tactical challenges are introduced across an additional 47 maps.
New Multiplayer maps, units, and abilitiesCreate your custom squad from a wider array of options, and dominate your opponent in intense, one-on-one, turn-based matches.