Dec 16 (Reuters) - Shares of Australian data centre landlord and operator DigiCo Infrastructure REIT DGT.AX extended declines in their second trading session on Monday, after marking the country's biggest initial public offering $(IPO.UK)$ in six years.

The stock was down 6.8% at A$4.24 as of 0318 GMT, after falling as much as 11.7% earlier in the session. It had an offer price of A$5.00.

DigiCo, which raised A$2 billion ($1.27 billion) in its IPO, the biggest since Viva Energy's VEA.AX A$2.65 billion listing in July 2018, is banking upon investor appetite for data centres, driven by the demand for artificial intelligence-based services.

However, investment research firm Morningstar last month gave DigiCo a "high uncertainty" rating, with a fair value estimate of A$3.40 per share.

DigiCo manages an A$4 billion portfolio of data centres across the United States and Australia. It said it will use part of the IPO proceeds to buy two large-scale adjoining data centre sites near Sydney with a contracted capacity of 20 megawatts.

Shares in asset manager HMC Capital HMC.AX, which retained an 18.2% stake in DigiCo after its listing, fell as much as 11.3%, making it the top loser on the benchmark .AXJO index, which was down 0.4%.

($1 = 1.5704 Australian dollars)

(Reporting by Aaditya Govind Rao in Bengaluru; Editing by Varun H K)

((Aaditya.GovindRao@thomsonreuters.com;))